%%
@article{fds339582,
Author = {Cecile, DJ and Chandrasekharan, S},
Title = {-Resonance and convergence of chiral perturbation
theory},
Journal = {Proceedings of Science},
Volume = {66},
Year = {2008},
Month = {January},
Abstract = {The dimensionless parameter′ = M2/(16π2F2), where F is
the pion decay constant in the chiral limit and M is the
pion mass at leading order in the quark mass, is expected to
control the convergence of chiral perturbation theory
applicable to QCD. Here we demonstrate that a strongly
coupled lattice gauge theory model with the same symmetries
as two-flavor QCD but with a much lighter -resonance is
different. Our model allows us to study efficiently the
convergence of chiral perturbation theory as a function of .
We first confirm that the leading low energy constants
appearing in the chiral Lagrangian are the same when
calculated from the -regime and the p-regime. However,′ .
0.002 is necessary before 1-loop chiral perturbation theory
predicts the data within 1%. However, for′ > 0.0035 the
data begin to deviate qualitatively from 1-loop chiral
perturbation theory predictions. We argue that this
qualitative change is due to the presence of a light
-resonance in our model. Our findings may be useful for
lattice QCD studies.},
Key = {fds339582}
}
@article{Chandrasekharan:2000dj,
Author = {Chandrasekharan Shailesh},
Title = {A chiral phase transition using a fermion cluster
algorithm},
Journal = {Chin. J. Phys.},
Volume = {38},
Number = {3},
Pages = {696-706},
Publisher = {PHYSICAL SOC REPUBLIC CHINA},
Year = {2000},
url = {http://arxiv.org/abs/hep-lat/0001003v1},
Abstract = {http://arxiv.org/abs/hep-lat/0001003},
Key = {Chandrasekharan:2000dj}
}
@article{Chandrasekharan:1996en,
Author = {Chandrasekharan, Shailesh},
Title = {A large N chiral transition on a plaquette},
Journal = {Phys. Lett. B},
Volume = {395},
Pages = {83-88},
Year = {1997},
url = {http://arxiv.org/pdf/hep-th/9610225},
Abstract = {http://arxiv.org/abs/hep-th/9610225},
Key = {Chandrasekharan:1996en}
}
@article{fds245728,
Author = {Chandrasekharan, S},
Title = {A LARGE N CHIRAL TRANSITION ON A PLAQUETTE},
Journal = {Phys. Lett. B},
Volume = {395},
Number = {1-2},
Pages = {83-88},
Publisher = {Elsevier BV},
Year = {1997},
url = {http://dx.doi.org/10.1016/S0370-2693(97)00050-6},
Abstract = {We construct a model of a chiral transition using the well
known large N transition in two dimensional U(N) lattice
gauge theory. Restricting the model to a single plaquette,
we introduce Grassmann variables on the corners of the
plaquette with the natural phase factors of staggered
fermions and couple them to the U(N) link variables. The
classical theory has a continuous chiral symmetry which is
broken at strong couplings, but is restored for weak
couplings in the $N \to \infty$ limit.},
Doi = {10.1016/S0370-2693(97)00050-6},
Key = {fds245728}
}
@article{Yoo:2004mh,
Author = {Yoo, J and Chandrasekharan, S and Baranger, HU},
Title = {A Multi-level Algorithm for Quantum-impurity
Models},
Journal = {Phys. Rev. E},
Volume = {71},
Number = {3 Pt 2B},
Pages = {036708},
Publisher = {cond-mat/0408123},
Year = {2005},
ISSN = {1539-3755},
url = {http://www.ncbi.nlm.nih.gov/pubmed/15903634},
Abstract = {A continuous-time path integral quantum Monte Carlo method
using the directed-loop algorithm is developed to simulate
the Anderson single-impurity model in the occupation number
basis. Although the method suffers from a sign problem at
low temperatures, the new algorithm has many advantages over
conventional algorithms. For example, the model can be
easily simulated in the Kondo limit without time
discretization errors. Furthermore, many observables
including the impurity susceptibility and a variety of
fermionic observables can be calculated efficiently. Finally
the new approach allows us to explore a general technique,
called the multilevel algorithm, to solve the sign problem.
We find that the multilevel algorithm is able to generate an
exponentially large number of configurations with an effort
that grows as a polynomial in inverse temperature such that
configurations with a positive sign dominate over those with
negative signs. Our algorithm can be easily generalized to
other multi-impurity problems.},
Doi = {10.1103/physreve.71.036708},
Key = {Yoo:2004mh}
}
@article{Chandrasekharan:2008gp,
Author = {Chandrasekharan, Shailesh},
Title = {A new computational approach to lattice quantum field
theories},
Journal = {PoS},
Volume = {LATTICE2008},
Pages = {003},
Year = {2008},
url = {http://arxiv.org/pdf/0810.2419},
Abstract = {http://arxiv.org/abs/0810.2419},
Key = {Chandrasekharan:2008gp}
}
@article{fds375116,
Author = {Maiti, S and Banerjee, D and Chandrasekharan, S and Marinkovic,
M},
Title = {A qubit regularization of asymptotic freedom at the BKT
transition without fine-tuning},
Journal = {Physical Review Letters},
Publisher = {American Physical Society},
Year = {2023},
Month = {July},
url = {http://dx.doi.org/10.48550/arXiv.2307.06117},
Abstract = {We propose a two-dimensional hard core loop-gas model as a
way to regularize the asymptotically free massive continuum
quantum field theory that emerges at the BKT transition.
Without fine-tuning, our model can reproduce the universal
step-scaling function of the classical lattice XY model in
the massive phase as we approach the phase transition. This
is achieved by lowering the fugacity of Fock-vacuum sites in
the loop-gas configuration space to zero in the
thermodynamic limit. Some of the universal quantities at the
BKT transition show smaller finite size effects in our model
as compared to the traditional XY model. Our model is a
prime example of qubit regularization of an asymptotically
free massive quantum field theory in Euclidean space-time
and helps understand how asymptotic freedom can arise as a
relevant perturbation at a decoupled fixed point without
fine-tuning.},
Doi = {10.48550/arXiv.2307.06117},
Key = {fds375116}
}
@article{fds245708,
Author = {Cecile, DJ and Chandrasekharan, S},
Title = {Absence of vortex condensation in a two dimensional
fermionic XY model},
Journal = {Phys. Rev. D},
Volume = {77},
Number = {5},
Pages = {054502},
Publisher = {American Physical Society (APS)},
Year = {2008},
ISSN = {1550-7998},
url = {http://link.aps.org/abstract/PRD/v77/e054502},
Abstract = {Motivated by a puzzle in the study of two dimensional
lattice Quantum Electrodynamics with staggered fermions, we
construct a two dimensional fermionic model with a global
$U(1)$ symmetry. Our model can be mapped into a model of
closed packed dimers and plaquettes. Although the model has
the same symmetries as the $XY$ model, we show numerically
that the model lacks the well known Kosterlitz-Thouless (KT)
phase transition. The model is always in the gapless phase
showing the absence of a phase with vortex condensation. In
other words the low energy physics is described by a
non-compact $U(1)$ field theory. We show that by introducing
an even number of layers one can introduce vortex
condensation within the model and thus also induce a KT
transition.},
Doi = {10.1103/PhysRevD.77.054502},
Key = {fds245708}
}
@article{Cecile:2008nb,
Author = {Cecile, D. J. and Chandrasekharan, Shailesh},
Title = {Absence of vortex condensation in a two dimensional
fermionic XY model},
Journal = {Phys. Rev.},
Volume = {D77},
Pages = {054502},
Year = {2008},
url = {http://arxiv.org/pdf/arXiv:0801.1857 [hep-lat]},
Abstract = {http://arxiv.org/abs/arXiv:0801.1857 [hep-lat]},
Key = {Cecile:2008nb}
}
@article{fds368438,
Author = {S. Chandrasekharan},
Title = {Acknowledgement to Reviewers of Condensed Matter in
2017},
Journal = {Condensed Matter},
Volume = {3},
Number = {1},
Pages = {3-3},
Publisher = {MDPI AG},
Year = {2018},
Month = {January},
url = {http://dx.doi.org/10.3390/condmat3010003},
Doi = {10.3390/condmat3010003},
Key = {fds368438}
}
@book{fds16196,
Author = {S. Chandrasekharan and U.-J. Wiese},
Title = {AN INTRODUCTION TO CHIRAL SYMMETRY ON THE
LATTICE},
Booktitle = {Prog. Part. Nucl. Phys. Vol. 53, issue 1,},
Year = {2004},
Key = {fds16196}
}
@article{Chandrasekharan:2004cn,
Author = {Chandrasekharan, S and Wiese, UJ},
Title = {An introduction to chiral symmetry on the
lattice},
Journal = {Prog. Part. Nucl. Phys.},
Volume = {53},
Number = {2},
Pages = {373-418},
Publisher = {Elsevier BV},
Year = {2004},
url = {http://arxiv.org/pdf/hep-lat/0405024},
Abstract = {http://arxiv.org/abs/hep-lat/0405024},
Doi = {10.1016/j.ppnp.2004.05.003},
Key = {Chandrasekharan:2004cn}
}
@article{Chandrasekharan:1998yx,
Author = {Chandrasekharan, Shailesh and others},
Title = {Anomalous chiral symmetry breaking above the QCD phase
transition},
Journal = {Phys. Rev. Lett.},
Volume = {82},
Pages = {2463-2466},
Year = {1999},
url = {http://arxiv.org/pdf/hep-lat/9807018},
Abstract = {http://arxiv.org/abs/hep-lat/9807018},
Key = {Chandrasekharan:1998yx}
}
@article{fds245739,
Author = {Chandrasekharan, S and Chen, D and Christ, N and Lee, W and Mawhinney,
R and Vranas, P},
Title = {ANOMALOUS CHIRAL SYMMETRY BREAKING ABOVE THE QCD PHASE
TRANSITION},
Journal = {Phys. Rev. Lett.},
Volume = {82},
Number = {12},
Pages = {2463-2466},
Publisher = {American Physical Society (APS)},
Year = {1999},
url = {http://dx.doi.org/10.1103/PhysRevLett.82.2463},
Abstract = {We study the anomalous breaking of U_A(1) symmetry just
above the QCD phase transition for zero and two flavors of
quarks, using a staggered fermion, lattice discretization.
The properties of the QCD phase transition are expected to
depend on the degree of U_A(1) symmetry breaking in the
transition region. For the physical case of two flavors, we
carry out extensive simulations on a 16^3 x 4 lattice,
measuring a difference in susceptibilities which is
sensitive to U_A(1) symmetry and which avoids many of the
staggered fermion discretization difficulties. The results
suggest that anomalous effects are at or below the 15%
level.},
Doi = {10.1103/PhysRevLett.82.2463},
Key = {fds245739}
}
@article{fds245714,
Author = {Chandrasekharan, S},
Title = {Anomalous Superconductivity in 2+1 dimensional two-color
lattice QCD},
Journal = {Phys. Rev. Lett.},
Volume = {97},
Number = {18},
Pages = {182001},
Year = {2006},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17155536},
Abstract = {We study thermodynamics of strongly coupled lattice QCD with
two colors of staggered fermions in 2+1 dimensions. The
partition function of this model can be written elegantly as
a statistical mechanics of dimers and baryon loops. The
model is invariant under an SO(3)×U(1) symmetry. At low
temperatures, we find evidence for superfluidity in the U(1)
symmetry sector while the SO(3) symmetry remains unbroken.
The finite temperature phase transition appears to belong to
the Kosterlitz-Thouless universality class, but the
superfluid density jump ρs(Tc) at the critical temperature
Tc is anomalously higher than the normal value of 2Tc/π. We
show that, by adding a small SO(3) symmetry breaking term to
the model, the superfluid density jump returns to its normal
value, implying that the extra symmetry causes anomalous
superfluid behavior. Our results may be of interest to
researchers studying superfluidity in spin-1
systems.},
Doi = {10.1103/physrevlett.97.182001},
Key = {fds245714}
}
@article{PhysRevLett.97.182001,
Author = {Chandrasekharan, Shailesh},
Title = {Anomalous Superfluidity in $(2+1)$-Dimensional Two-Color
Lattice QCD},
Journal = {Phys. Rev. Lett.},
Volume = {97},
Number = {18},
Pages = {182001},
Year = {2006},
Key = {PhysRevLett.97.182001}
}
@article{fds245682,
Author = {Chandrasekharan, S and Li, A},
Title = {Anomaly and a QCD-like phase diagram with massive bosonic
baryons},
Journal = {Journal of High Energy Physics},
Volume = {12},
Number = {021},
Publisher = {Springer Nature},
Year = {2010},
ISSN = {1126-6708},
url = {http://www.springerlink.com/content/f44x269565536614/},
Abstract = {We study a strongly coupled Z2 lattice gauge theory with two
flavors of quarks, invariant under an exact SU(2)×SU(2)×U
A(1)×UB(1) symmetry which is the same as in QCD with two
flavors of quarks without an anomaly. The model also
contains a coupling that can be used to break the UA(1)
symmetry and thus mimic the QCD anomaly. At low temperatures
T and small baryon chemical potential μB the model contains
massless pions and massive bosonic baryons similar to QCD
with an even number of colors. In this work we study the T -
μB phase diagram of the model and show that it contains
three phases: (1) A chirally broken phase at low T and μB,
(2) a chirally symmetric baryon superfluid phase at low T
and high μB, and (3) a symmetric phase at high T. We find
that the nature of the finite temperature chiral phase
transition and in particular the location of the tricritical
point that seperates the first order line from the second
order line is affected significantly by the anomaly. © 2010
SISSA.},
Doi = {10.1007/JHEP12(2010)021},
Key = {fds245682}
}
@article{Chandrasekharan:1993ag,
Author = {Chandrasekharan, Shailesh},
Title = {Anomaly cancellation in (2+1)-dimensions in the presence of
a domain wall mass},
Journal = {Phys. Rev. D},
Volume = {49},
Pages = {1980-1987},
Year = {1994},
url = {http://arxiv.org/pdf/hep-th/9311050},
Abstract = {http://arxiv.org/abs/hep-th/9311050},
Key = {Chandrasekharan:1993ag}
}
@article{fds245735,
Author = {Chandrasekharan, S},
Title = {ANOMALY CANCELLATION IN (2+1)-DIMENSIONS IN THE PRESENCE OF
A DOMAIN WALL MASS},
Journal = {Phys. Rev. D},
Volume = {49},
Number = {4},
Pages = {1980-1987},
Year = {1994},
ISSN = {0556-2821},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10017182},
Abstract = {A fermion in 2+1 dimensions, with a mass function which
depends on one spatial coordinate and passes through a zero
(a domain wall mass), in the background of an Abelian gauge
field is considered. In this model, originally proposed in a
non-Abelian version by Callan and Harvey, the gauge
variation of the effective gauge action mainly consists of
two terms. One comes from the induced Chern-Simons term and
the other from the chiral fermions, bound to the
(1+1)-dimensional wall, and they are expected to cancel each
other. Though there exist arguments in favor of this, based
on the possible forms of the effective action valid far from
the wall and some facts about theories of chiral fermions in
1+1 dimensions, a complete calculation is lacking. In this
paper we present an explicit calculation of this
cancellation at one loop which is valid even close to the
wall. We show that integrating out the ``massive'' modes of
the theory does produce the Chern-Simons term, as
appreciated previously. In addition, we show that it
generates a term that softens the high energy behavior of
the (1+1)-dimensional effective chiral theory thereby
resolving an ambiguity present in a general
(1+1)-dimensional theory.},
Doi = {10.1103/physrevd.49.1980},
Key = {fds245735}
}
@article{fds375525,
Author = {Maiti, S and Banerjee, D and Chandrasekharan, S and Marinkovic,
MK},
Title = {Asymptotic Freedom at the Berezinskii-Kosterlitz-Thouless
Transition without Fine-Tuning Using a Qubit
Regularization.},
Journal = {Physical review letters},
Volume = {132},
Number = {4},
Pages = {041601},
Publisher = {American Physical Society (APS)},
Year = {2024},
Month = {January},
url = {http://dx.doi.org/10.1103/physrevlett.132.041601},
Abstract = {We propose a two-dimensional hard-core loop-gas model as a
way to regularize the asymptotically free massive continuum
quantum field theory that emerges at the
Berezinskii-Kosterlitz-Thouless transition. Without
fine-tuning, our model can reproduce the universal
step-scaling function of the classical lattice XY model in
the massive phase as we approach the phase transition. This
is achieved by lowering the fugacity of Fock-vacuum sites in
the loop-gas configuration space to zero in the
thermodynamic limit. Some of the universal quantities at the
Berezinskii-Kosterlitz-Thouless transition show smaller
finite size effects in our model as compared to the
traditional XY model. Our model is a prime example of qubit
regularization of an asymptotically free massive quantum
field theory in Euclidean space-time and helps understand
how asymptotic freedom can arise as a relevant perturbation
at a decoupled fixed point without fine-tuning.},
Doi = {10.1103/physrevlett.132.041601},
Key = {fds375525}
}
@article{fds347440,
Author = {Chandrasekharan, S and Orasch, O and Gattringer, C and Torek,
P},
Title = {Baryon bag simulation of QCD in the strong coupling
limit},
Journal = {PoS LATTICE2019 (2019) 117},
Publisher = {arXiv.org},
Year = {2020},
Month = {August},
url = {http://dx.doi.org/10.22323/1.363.0117},
Abstract = {We explore the possibility of a simulation of strong
coupling QCD in terms of so-called baryon bags. In this form
the known representation in terms of monomers, dimers and
baryon loops is reorganized such that the baryon
contributions are collected in space time domains referred
to as baryon bags. Within the bags three quarks propagate
coherently as a baryon that is described by a free fermion,
whereas the rest of the lattice is solely filled with
interacting meson terms, i.e., quark and diquark monomers
and dimers. We perform a simulation directly in the baryon
bag language using a newly developed worm update and show
first results in two dimensions.},
Doi = {10.22323/1.363.0117},
Key = {fds347440}
}
@article{fds354953,
Author = {Orasch, O and Chandrasekharan, S and Gattringer, C and Törek,
P},
Title = {Baryon bag simulation of QCD in the strong coupling
limit},
Journal = {Proceedings of Science},
Volume = {363},
Year = {2019},
Month = {January},
Abstract = {We explore the possibility of a simulation of strong
coupling QCD in terms of so-called baryon bags. In this form
the known representation in terms of monomers, dimers and
baryon loops is reorganized such that the baryon
contributions are collected in space time domains referred
to as baryon bags. Within the bags three quarks propagate
coherently as a baryon that is described by a free fermion,
whereas the rest of the lattice is solely filled with
interacting meson terms, i.e., quark and diquark monomers
and dimers. We perform a simulation directly in the baryon
bag language using a newly developed worm update and show
first results in two dimensions.},
Key = {fds354953}
}
@article{fds336985,
Author = {Ayyar, V and Chandrasekharan, S and Rantaharju,
J},
Title = {Benchmark results in the 2D lattice Thirring model with a
chemical potential},
Volume = {97},
Number = {5},
Year = {2018},
Month = {March},
url = {http://dx.doi.org/10.1103/PhysRevD.97.054501},
Abstract = {We study the two-dimensional lattice Thirring model in the
presence of a fermion chemical potential. Our model is
asymptotically free and contains massive fermions that mimic
a baryon and light bosons that mimic pions. Hence, it is a
useful toy model for QCD, especially since it, too, suffers
from a sign problem in the auxiliary field formulation in
the presence of a fermion chemical potential. In this work,
we formulate the model in both the world line and
fermion-bag representations and show that the sign problem
can be completely eliminated with open boundary conditions
when the fermions are massless. Hence, we are able
accurately compute a variety of interesting quantities in
the model, and these results could provide benchmarks for
other methods that are being developed to solve the sign
problem in QCD.},
Doi = {10.1103/PhysRevD.97.054501},
Key = {fds336985}
}
@article{Chandrasekharan:2003ug,
Author = {Chandrasekharan Shailesh},
Title = {Chiral and critical behavior in strong coupling
QCD},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {129},
Pages = {578-580},
Publisher = {Elsevier BV},
Year = {2004},
url = {http://arxiv.org/pdf/hep-lat/0309098},
Abstract = {http://arxiv.org/abs/hep-lat/0309098},
Doi = {10.1016/S0920-5632(03)02647-1},
Key = {Chandrasekharan:2003ug}
}
@article{Chandrasekharan:2005dn,
Author = {Chandrasekharan, S and Jiang, F-J},
Title = {Chiral limit of 2-color QCD at strong couplings},
Journal = {PoS},
Volume = {LAT2005},
Pages = {198},
Year = {2006},
url = {http://arxiv.org/abs/hep-lat/0509117v1},
Abstract = {http://arxiv.org/abs/hep-lat/0509117},
Key = {Chandrasekharan:2005dn}
}
@article{fds29982,
Author = {S. Chandrasekharan},
Title = {CHIRAL LIMIT OF STAGGERED FERMIONS AT STRONG COUPLINGS: A
LOOP REPRESENTATION},
Journal = {Nucl. Phys. B (Proceedings Suppl.)},
Volume = {119},
Pages = {929},
Editor = {Edwards, Negele and Richards},
Year = {2003},
Abstract = {The partition function of two dimensional massless staggered
fermions interacting with U(N) gauge fields is rewritten in
terms of loop variables in the strong coupling limit. We use
this representation of the theory to devise a non-local
Metropolis algorithm to calculate the chiral susceptibility.
For small lattices our algorithm reproduces exact results
quite accurately. Applying this algorithm to large volumes
yields rather surprising results. In particular we find
$m_\pi \neq 0$ for all $N$ and it increases with $N$. Since
the talk was presented we have found reasons to believe that
our algorithm breaks down for large volumes questioning the
validity of our results.},
Key = {fds29982}
}
@article{Chandrasekharan:2002gp,
Author = {Chandrasekharan Shailesh},
Title = {Chiral limit of staggered fermions at strong couplings: A
loop representation},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {119},
Pages = {929-931},
Publisher = {Elsevier BV},
Year = {2003},
url = {http://arxiv.org/pdf/hep-lat/0208071},
Abstract = {http://arxiv.org/abs/hep-lat/0208071},
Doi = {10.1016/S0920-5632(03)01722-5},
Key = {Chandrasekharan:2002gp}
}
@article{Adams:2003cc,
Author = {Adams, David H. and Chandrasekharan, Shailesh},
Title = {Chiral limit of strongly coupled lattice gauge
theories},
Journal = {Nucl. Phys. B},
Volume = {662},
Pages = {220-246},
Year = {2003},
url = {http://arxiv.org/pdf/hep-lat/0303003},
Abstract = {http://arxiv.org/abs/hep-lat/0303003},
Key = {Adams:2003cc}
}
@article{fds245722,
Author = {Adams, DH and Chandrasekharan, S},
Title = {CHIRAL LIMIT OF STRONGLY COUPLED LATTICE GAUGE
THEORIES},
Journal = {Nucl. Phys. B},
Volume = {662},
Number = {1-2},
Pages = {220-246},
Publisher = {Elsevier BV},
Year = {2003},
url = {http://dx.doi.org/10.1016/S0550-3213(03)00350-X},
Abstract = {We construct a new and efficient cluster algorithm for
updating strongly coupled U(N) lattice gauge theories with
staggered fermions in the chiral limit. The algorithm uses
the constrained monomer-dimer representation of the theory
and should also be of interest to researchers working on
other models with similar constraints. Using the new
algorithm we address questions related to the chiral limit
of strongly coupled U(N) gauge theories beyond the mean
field approximation. We show that the infinite volume chiral
condensate is non-zero in three and four dimensions.
However, on a square lattice of size $L$ we find $\sum_x
\sim L^{2-\eta}$ for large $L$ where $\eta = 0.420(3)/N +
0.078(4)/N^2$. These results differ from an earlier
conclusion obtained using a different algorithm. Here we
argue that the earlier calculations were misleading due to
uncontrolled autocorrelation times encountered by the
previous algorithm.},
Doi = {10.1016/S0550-3213(03)00350-X},
Key = {fds245722}
}
@article{Chandrasekharan:2003im,
Author = {Chandrasekharan, Shailesh and Jiang, Fu-Jiun},
Title = {Chiral limit of strongly coupled lattice QCD at finite
temperatures},
Journal = {Phys. Rev. D},
Volume = {68},
Pages = {091501},
Year = {2003},
url = {http://arxiv.org/pdf/hep-lat/0309025},
Abstract = {http://arxiv.org/abs/hep-lat/0309025},
Key = {Chandrasekharan:2003im}
}
@article{fds245719,
Author = {Chandrasekharan, S and Jiang, F-J},
Title = {CHIRAL LIMIT OF STRONGLY COUPLED LATTICE QCD AT FINITE
TEMPERATURES},
Journal = {Physical Reviews D (Rapid Communications)},
Volume = {68},
Number = {9},
Pages = {091501},
Year = {2003},
ISSN = {0556-2821},
url = {http://dx.doi.org/10.1103/PhysRevD.68.091501},
Abstract = {We use the recently proposed directed-path algorithm to
study the chiral limit of a strongly coupled lattice QCD
with staggered quarks at finite temperatures. The new
algorithm allows us to compute the chiral susceptibility and
the pion decay constant accurately on large lattices for
massless quarks. In the low temperature phase we find clear
evidence for the singularities predicted by chiral
perturbation theory. We also show convincingly that the
chiral phase transition is of second order and belongs to
the O(2) universality class. © The American Physical
Society.},
Doi = {10.1103/PhysRevD.68.091501},
Key = {fds245719}
}
@article{PhysRevB.71.201309,
Author = {Yoo, J and Chandrasekharan, S and Kaul, RK and Ullmo, D and Baranger,
HU},
Title = {Cluster Algorithms for Quantum Impurity Models and
Mesoscopic Kondo Physics},
Journal = {Phys. Rev. B},
Volume = {71},
Number = {20},
Pages = {201309(R)},
Publisher = {cond-mat/0411313},
Year = {2005},
url = {http://dx.doi.org/10.1103/PhysRevB.71.201309},
Abstract = {Nanoscale physics and dynamical mean-field theory have both
generated increased interest in complex quantum impurity
problems and so have focused attention on the need for
flexible quantum impurity solvers. Here we demonstrate that
the mapping of single-quantum impurity problems onto spin
chains can be exploited to yield a powerful and extremely
flexible impurity solver. We implement this cluster
algorithm explicitly for the Anderson and Kondo
Hamiltonians, and illustrate its use in the "mesoscopic
Kondo problem." To study universal Kondo physics, a large
ratio between the effective bandwidth Deff and the
temperature T is required; our cluster algorithm treats the
mesoscopic fluctuations exactly while being able to approach
the large Deff T limit with ease. We emphasize that the
flexibility of our method allows it to tackle a wide variety
of quantum impurity problems; thus, it may also be relevant
to the dynamical mean-field theory of lattice problems. ©
2005 The American Physical Society.},
Doi = {10.1103/PhysRevB.71.201309},
Key = {PhysRevB.71.201309}
}
@article{fds245684,
Author = {Liu, D and Chandrasekharan, S and Baranger, HU},
Title = {Conductance of quantum impurity models from quantum Monte
Carlo},
Journal = {Physical Review B},
Volume = {82},
Number = {16},
Pages = {165447},
Publisher = {American Physical Society (APS)},
Year = {2010},
ISSN = {1098-0121},
url = {http://hdl.handle.net/10161/4258 Duke open
access},
Abstract = {The conductance of two Anderson impurity models, one with
twofold and another with fourfold degeneracy, representing
two types of quantum dots, is calculated using a world-line
quantum Monte Carlo (QMC) method. Extrapolation of the
imaginary time QMC data to zero frequency yields the linear
conductance, which is then compared to numerical
renormalization-group results in order to assess its
accuracy. We find that the method gives excellent results at
low temperature (T TK) throughout the mixed-valence and
Kondo regimes but it is unreliable for higher temperature.
© 2010 The American Physical Society.},
Doi = {10.1103/PhysRevB.82.165447},
Key = {fds245684}
}
@article{Chandrasekharan:1998ck,
Author = {Chandrasekharan, Shailesh},
Title = {Confinement, chiral symmetry breaking and continuum limits
in quantum link models},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {73},
Pages = {739-741},
Year = {1999},
url = {http://arxiv.org/pdf/hep-lat/9809084},
Abstract = {http://arxiv.org/abs/hep-lat/9809084},
Key = {Chandrasekharan:1998ck}
}
@article{fds245738,
Author = {Chandrasekharan, S},
Title = {CONFINEMENT, CHIRAL SYMMETRY BREAKING AND CONTINUUM LIMITS
IN QUANTUM LINK MODELS},
Journal = {Nucl. Phys. B Proc. Suppl.},
Volume = {73},
Number = {1-3},
Pages = {739-741},
Publisher = {Elsevier BV},
Year = {1999},
url = {http://dx.doi.org/10.1016/S0920-5632(99)85189-5},
Abstract = {Using the example of compact U(1) lattice gauge theory we
argue that quantum link models can be used to reproduce the
physics of conventional Hamiltonian lattice gauge theories.
In addition to the usual gauge coupling g, these models have
a new parameter j which naturally cuts-off large electric
flux quanta on each link while preserving exact U(1) gauge
invariance. The j → ∞ limit recovers the conventional
Hamiltonian. At strong couplings, the theory shows
confinement and chiral symmetry breaking for all non-trivial
values of j. The phase diagram of the 3+1 dimensional theory
suggests that a coulomb phase is present at large but finite
j. Setting g = 0, a new approach to the physics of compact
U(1) gauge theory on the lattice emerges. In this case the
parameter j takes over the role of the gauge coupling, and j
→ ∞ describes free photons.},
Doi = {10.1016/S0920-5632(99)85189-5},
Key = {fds245738}
}
@article{fds345675,
Author = {Banerjee, D and Chandrasekharan, S and Orlando, D and Reffert,
S},
Title = {Conformal Dimensions in the Large Charge Sectors at the O(4)
Wilson-Fisher Fixed Point.},
Journal = {Physical review letters},
Volume = {123},
Number = {5},
Pages = {051603},
Year = {2019},
Month = {August},
url = {http://dx.doi.org/10.1103/physrevlett.123.051603},
Abstract = {We study the O(4) Wilson-Fisher fixed point in 2+1
dimensions in fixed large-charge sectors identified by
products of two spin-j representations (j_{L},j_{R}). Using
effective field theory we derive a formula for the conformal
dimensions D(j_{L},j_{R}) of the leading operator in terms
of two constants, c_{3/2} and c_{1/2}, when the sum
j_{L}+j_{R} is much larger than the difference
|j_{L}-j_{R}|. We compute D(j_{L},j_{R}) when j_{L}=j_{R}
with Monte Carlo calculations in a discrete formulation of
the O(4) lattice field theory, and show excellent agreement
with the predicted formula and estimate c_{3/2}=1.068(4) and
c_{1/2}=0.083(3).},
Doi = {10.1103/physrevlett.123.051603},
Key = {fds345675}
}
@article{fds332870,
Author = {Banerjee, D and Chandrasekharan, S and Orlando,
D},
Title = {Conformal dimensions via large charge expansion},
Volume = {120},
Number = {6},
Pages = {061603},
Year = {2018},
Month = {February},
url = {http://dx.doi.org/10.1103/physrevlett.120.061603},
Abstract = {We construct an efficient Monte Carlo algorithm that
overcomes the severe signal-to-noise ratio problems and
helps us to accurately compute the conformal dimensions of
large-Q fields at the Wilson-Fisher fixed point in the O(2)
universality class. Using it we verify a recent proposal
that conformal dimensions of strongly coupled conformal
field theories with a global U(1) charge can be obtained via
a series expansion in the inverse charge 1/Q. We find that
the conformal dimensions of the lowest operator with a fixed
charge Q are almost entirely determined by the first few
terms in the series.},
Doi = {10.1103/physrevlett.120.061603},
Key = {fds332870}
}
@article{Chandrasekharan:2004kd,
Author = {Chandrasekharan, Shailesh and Strouthos, Costas
G.},
Title = {Connecting lattice QCD with chiral perturbation theory at
strong coupling},
Journal = {Phys. Rev. D},
Volume = {69},
Pages = {091502},
Year = {2004},
url = {http://arxiv.org/pdf/hep-lat/0401002},
Abstract = {http://arxiv.org/abs/hep-lat/0401002},
Key = {Chandrasekharan:2004kd}
}
@article{fds245720,
Author = {Chandrasekharan, S and Strouthos, CG},
Title = {CONNECTING LATTICE QCD WITH CHIRAL PERTURBATION THEORY AT
STRONG COUPLING},
Journal = {Physical Review (Rapid Communications)},
Volume = {D69},
Number = {9},
Pages = {091502},
Publisher = {American Physical Society (APS)},
Year = {2004},
ISSN = {0556-2821},
url = {http://dx.doi.org/10.1103/PhysRevD.69.091502},
Abstract = {We study the difficulties associated with detecting chiral
singularities predicted by chiral perturbation theory (ChPT)
in lattice QCD. We focus on the physics of the remnant O(2)
chiral symmetry of staggered fermions in the strong coupling
limit using the recently discovered directed path algorithm.
Since it is easier to look for powerlike singularities as
compared to logarithmic ones, our calculations are performed
at a fixed finite temperature in the chirally broken phase.
We show that the behavior of the chiral condensate, the pion
mass, and the pion decay constant are all consistent with
the predictions of ChPT for small masses. However, in order
to demonstrate this we need quark masses that are much
smaller (in lattice units) than those typically used in
dynamical QCD simulations. We also need to use higher order
terms in the chiral expansion to fit our data. © 2004 The
American Physical Society.},
Doi = {10.1103/PhysRevD.69.091502},
Key = {fds245720}
}
@article{Chandrasekharan:2003eu,
Author = {Chandrasekharan, S.},
Title = {Connections between quantum chromodynamics and condensed
matter physics},
Journal = {Pramana},
Volume = {61},
Pages = {901-910},
Year = {2003},
Key = {Chandrasekharan:2003eu}
}
@article{fds245716,
Author = {Chandrasekharan, S},
Title = {CONNECTIONS BETWEEN QUANTUM CHROMODYNAMICS AND CONDENSED
MATTER PHYSICS},
Journal = {Pramana},
Volume = {61},
Number = {5},
Pages = {901},
Publisher = {Springer Nature},
Year = {2003},
url = {http://dx.doi.org/10.1007/BF02704458},
Abstract = {Features of QCD can be seen qualitatively in certain
condensed matter systems. Recently some of the analyses that
originated in condensed matter physics have found
applications in QCD. Using examples we discuss some of the
connections between the two fields and show how progress can
be made by exploiting this connection. Some of the
challenges that remain in the two fields are quite similar.
We argue that recent algorithmic developments call for
optimism in both fields.},
Doi = {10.1007/BF02704458},
Key = {fds245716}
}
@article{Chandrasekharan:1994kx,
Author = {Chandrasekharan, S.},
Title = {CRITICAL BEHAVIOR AT THE QCD PHASE TRANSITION WITH TWO
MASSLESS QUARK FLAVORS},
Booktitle = {Continuous Advances in QCD},
Publisher = {World Scientific},
Editor = {Smilga, A.V.},
Year = {1994},
Key = {Chandrasekharan:1994kx}
}
@book{fds4165,
Author = {S. Chandrasekharan},
Title = {CRITICAL BEHAVIOR AT THE QCD PHASE TRANSITION WITH TWO
MASSLESS QUARK FLAVORS},
Booktitle = {Continuous Advances in QCD},
Publisher = {World Scientific},
Editor = {Andrei V. Smilga},
Year = {1994},
Key = {fds4165}
}
@article{Chandrasekharan:2000rm,
Author = {Chandrasekharan, Shailesh and Osborn, James
C.},
Title = {Critical behavior of a chiral condensate with a meron
cluster algorithm},
Journal = {Phys. Lett. B},
Volume = {496},
Pages = {122-128},
Year = {2000},
url = {http://arxiv.org/pdf/hep-lat/0010036},
Abstract = {http://arxiv.org/abs/hep-lat/0010036},
Key = {Chandrasekharan:2000rm}
}
@article{fds245742,
Author = {Chandrasekharan, S and Osborn, JC},
Title = {CRITICAL BEHAVIOR OF A CHIRAL CONDENSATE WITH A MERON
CLUSTER ALGORITHM.},
Journal = {Phys. Letts. B},
Volume = {496},
Number = {1-2},
Pages = {122-128},
Publisher = {Elsevier BV},
Year = {2000},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/S0370-2693(00)01294-6},
Abstract = {A new meron cluster algorithm is constructed to study the
finite temperature critical behavior of the chiral
condensate in a $(3+1)$ dimensional model of interacting
staggered fermions. Using finite size scaling analysis the
infinite volume condensate is shown to be consistent with
the behavior of the form $(T_c-T)^{0.314(7)}$ for
temperatures less than the critical temperature and
$m^{1/4.87(10)}$ at the critical temperature confirming that
the critical behavior belongs to the 3-d Ising universality
class within one to two sigma deviation. The new method,
along with improvements in the implementation of the
algorithm, allows the determination of the critical
temperature $T_c$ more accurately than was possible in a
previous study.},
Doi = {10.1016/S0370-2693(00)01294-6},
Key = {fds245742}
}
@article{Chandrasekharan:1994cq,
Author = {Chandrasekharan, Shailesh},
Title = {Critical behavior of the chiral condensate at the QCD phase
transition},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {42},
Pages = {475-477},
Year = {1995},
url = {http://arxiv.org/pdf/hep-lat/9412070},
Abstract = {http://arxiv.org/abs/hep-lat/9412070},
Key = {Chandrasekharan:1994cq}
}
@article{fds245734,
Author = {Chandrasekharan, S},
Title = {CRITICAL BEHAVIOR OF THE CHIRAL CONDENSATE AT THE QCD PHASE
TRANSITION},
Journal = {Nucl. Phys. B (Proc. Suppl.)},
Volume = {42},
Number = {1-3},
Pages = {475-477},
Publisher = {Elsevier BV},
Year = {1995},
ISSN = {0920-5632},
url = {http://dx.doi.org/10.1016/0920-5632(95)00284-G},
Abstract = {We study the critical behavior of the chiral condensate near
the QCD phase transition in the background of two fixed
light dynamical (sea) quarks. We study the condensate for
$5.245 \leq \beta \leq 5.3$ and $10^{-10} \leq m_{val} \leq
10$},
Doi = {10.1016/0920-5632(95)00284-G},
Key = {fds245734}
}
@article{fds245717,
Author = {Brower, R and Chandrasekharan, S and Riederer, S and Wiese,
UJ},
Title = {D THEORY: FIELD QUANTIZATION BY DIMENSIONAL REDUCTION OF
DISCRETE VARIABLES},
Journal = {Nucl. Phys. B},
Volume = {693},
Number = {1-3},
Pages = {149},
Year = {2004},
url = {http://dx.doi.org/10.1016/S0920-5632(97)00900-6},
Abstract = {A new non-perturbative approach to quantum field theory -
D-theory - is proposed, in which continuous classical fields
are replaced by discrete quantized variables which undergo
dimensional reduction. The 2-d classical O(3) model emerges
from the (2 + 1)-d quantum Heisenberg model formulated in
terms of quantum spins. Dimensional reduction is
demonstrated explicitly by simulating correlation lengths up
to 350,000 lattice spacings using a loop cluster algorithm.
In the framework of D-theory, gauge theories are formulated
in terms of quantum links - the gauge analogs of quantum
spins. Quantum links are parallel transporter matrices whose
elements are non-commuting operators. They can be expressed
as bilinears of anticommuting fermion constituents. In
quantum link models dimensional reduction to four dimensions
occurs, due to the presence of a 5-d Coulomb phase, whose
existence is confirmed by detailed simulations using
standard lattice gauge theory. Using Shamir's variant of
Kaplan's fermion proposal, in quantum link QCD quarks appear
as edge states of a 5-d slab. This naturally protects their
chiral symmetries without fine-tuning. The first efficient
cluster algorithm for a gauge theory with a continuous gauge
group is formulated for the U(1) quantum link model.
Improved estimators for Wilson loops are constructed, and
dimensional reduction to ordinary lattice QED is verified
numerically.},
Doi = {10.1016/S0920-5632(97)00900-6},
Key = {fds245717}
}
@article{Brower:2003vy,
Author = {Brower, R. and Chandrasekharan, S. and Riederer, S. and Wiese, U. J.},
Title = {D-theory: Field quantization by dimensional reduction of
discrete variables},
Journal = {Nucl. Phys. B},
Volume = {693},
Pages = {149-175},
Year = {2004},
url = {http://arxiv.org/pdf/hep-lat/0309182},
Abstract = {http://arxiv.org/abs/hep-lat/0309182},
Key = {Brower:2003vy}
}
@article{Beard:1997ic,
Author = {Beard, B. B. and others},
Title = {D-theory: Field theory via dimensional reduction of discrete
variables},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {63},
Pages = {775-789},
Year = {1998},
url = {http://arxiv.org/pdf/hep-lat/9709120},
Abstract = {http://arxiv.org/abs/hep-lat/9709120},
Key = {Beard:1997ic}
}
@article{fds245724,
Author = {Beard, BB and Brower, RC and Chandrasekharan, S and Chen, D and Tsapalis, A and Wiese, UJ},
Title = {D-THEORY: FIELD THEORY VIA DIMENSIONAL REDUCTION OF DISCRETE
VARIABLES},
Journal = {Nucl. Phys. B (Proc. Suppl.)},
Volume = {63},
Number = {1-3},
Pages = {775-789},
Publisher = {Elsevier BV},
Year = {1998},
url = {http://dx.doi.org/10.1016/j.nuclphysb.2004.06.007},
Abstract = {A new non-perturbative approach to quantum field theory ---
D-theory --- is proposed, in which continuous classical
fields are replaced by discrete quantized variables which
undergo dimensional reduction. The 2-d classical O(3) model
emerges from the (2+1)-d quantum Heisenberg model formulated
in terms of quantum spins. Dimensional reduction is
demonstrated explicitly by simulating correlation lengths up
to 350,000 lattice spacings using a loop cluster algorithm.
In the framework of D-theory, gauge theories are formulated
in terms of quantum links --- the gauge analogs of quantum
spins. Quantum links are parallel transporter matrices whose
elements are non-commuting operators. They can be expressed
as bilinears of anticommuting fermion constituents. In
quantum link models dimensional reduction to four dimensions
occurs, due to the presence of a 5-d Coulomb phase, whose
existence is confirmed by detailed simulations using
standard lattice gauge theory. Using Shamir's variant of
Kaplan's fermion proposal, in quantum link QCD quarks appear
as edge states of a 5-d slab. This naturally protects their
chiral symmetries without fine-tuning. The first efficient
cluster algorithm for a gauge theory with a continuous gauge
group is formulated for the U(1) quantum link model.
Improved estimators for Wilson loops are constructed, and
dimensional reduction to ordinary lattice QED is verified
numerically.},
Doi = {10.1016/j.nuclphysb.2004.06.007},
Key = {fds245724}
}
@article{Chandrasekharan:1995gt,
Author = {Chandrasekharan, Shailesh and Christ, Norman
H.},
Title = {Dirac Spectrum, Axial Anomaly and the QCD Chiral Phase
Transition},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {47},
Pages = {527-534},
Year = {1996},
url = {http://arxiv.org/pdf/hep-lat/9509095},
Abstract = {http://arxiv.org/abs/hep-lat/9509095},
Key = {Chandrasekharan:1995gt}
}
@article{fds245732,
Author = {Chandrasekharan, S and Christ, N},
Title = {DIRAC SPECTRUM, AXIAL ANOMALY AND THE QCD CHIRAL PHASE
TRANSITION},
Journal = {NUcl. Phys. B (Proc. Suppl.)},
Volume = {47},
Number = {1-3},
Pages = {527-534},
Publisher = {Elsevier BV},
Year = {1996},
url = {http://dx.doi.org/10.1016/0920-5632(96)00115-6},
Abstract = {The QCD phase transition is studied on $16^3$ and $32^3
\times 4$ lattices both with and without quark loops. We
introduce a new zero-flavor or quenched species of quark
$\zeta$ and study the resulting chiral condensate, $\azbz$
as a function of the $\zeta$ mass, $m_\zeta$. By examining
$\azbz$ for $10^{-10} \le m_\zeta \le 10$ we gain
considerable information about the spectrum of Dirac
eigenvalues. A comparison of $ma=0.01$ and 0.025 shows
little dependence of the Dirac spectrum on such a light,
dynamical quark mass, after an overall shift in $\beta$ is
removed. The presence of sufficient small eigenvalues to
support anomalous chiral symmetry breaking in the high
temperature phase is examined quantitatively. In an effort
to enhance these small eigenvalues, $\azbz$ is also examined
in the pure gauge theory in the region of the deconfinement
transition with unexpected results. Above the critical
temperature, the three $Z_3$ phases show dramatically
different chiral behavior. Surprisingly, the real phase
shows chiral symmetry, suggesting that a system with one
flavor of staggered fermion at $N_t=4$ will possess a chiral
a phase transition---behavior not expected in the continuum
limit.},
Doi = {10.1016/0920-5632(96)00115-6},
Key = {fds245732}
}
@article{fds303651,
Author = {Lee, JW and Chandrasekharan, S and Baranger, HU},
Title = {Disorder-Induced Superfluidity in Hardcore Bosons in Two
Dimensions},
Journal = {Phys. Rev. B},
Year = {2007},
url = {http://arxiv.org/abs/cond-mat/0611109v1},
Abstract = {We study the effect of disorder on hardcore bosons in two
dimensions at the SU(2) symmetric ``Heisenberg point''. We
obtain our results with quantum Monte Carlo simulations
using the directed loop algorithm. In the absence of
disorder, the system has no long-range order at finite
temperature due to the enhanced symmetry. However, the
introduction of a disordered potential, uniformly
distributed from -D to D, induces a finite-temperature
superfluid phase. In particular the diagonal correlation
length \xi decreases but the superfluid order-parameter
correlation function becomes a power-law. A non-monotonic
finite-size behavior is noted and explained as arising due
to \xi. We provide evidence that at long distances the
effects of a weak disordered potential can be mimicked by an
effective uniform potential with a root-mean-square value:
mu_eff = D/sqrt{3}. For strong disorder, the system becomes
a Bose glass insulator.},
Key = {fds303651}
}
@article{lee-2006,
Author = {Lee, Ji-Woo and Chandrasekharan, Shailesh and Baranger,
Harold U.},
Title = {Disorder-Induced Superfluidity in Hardcore Bosons in Two
Dimensions},
Year = {2006},
url = {http://arxiv.org/pdf/arXiv:0705.0617 [hep-lat]},
Abstract = {http://arxiv.org/abs/arXiv:0705.0617 [hep-lat]},
Key = {lee-2006}
}
@article{fds245712,
Author = {Chandrasekharan, S and Mehta, AC},
Title = {Effects of the anomaly on the QCD chiral phase
transition},
Journal = {Proceedings of Science},
Volume = {LAT2006},
Number = {14},
Pages = {128},
Year = {2006},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17930663},
Abstract = {We use strongly coupled lattice QED with two flavors of
massless staggered fermions to model the chiral phase
transition in two-flavor massless QCD. Our model allows us
to vary the QCD anomaly and thus study its effects on the
transition. Our study confirms the widely accepted viewpoint
that the chiral phase transition is first order in the
absence of the anomaly. Turning on the anomaly weakens the
transition and turns it second order at a critical anomaly
strength. The anomaly strength at the tricritical point is
characterized using r=(M(eta')-M(pi))/rho(eta'), where
M(eta'), M(pi) are the screening masses of the anomalous and
regular pions and rho(eta') is the mass scale that governs
the low energy fluctuations of the anomalous symmetry. We
estimate that r ~ 7 in our model. This suggests that a
strong anomaly at the two-flavor QCD chiral phase transition
is necessary to wash out the first order
transition.},
Doi = {10.1103/physrevlett.99.142004},
Key = {fds245712}
}
@article{Chandrasekharan:2007up,
Author = {Chandrasekharan, Shailesh and Mehta, Abhijit
C.},
Title = {Effects of the anomaly on the two-flavor QCD chiral phase
transition},
Journal = {Phys. Rev. Lett.},
Volume = {99},
Pages = {142004},
Year = {2007},
url = {http://arxiv.org/pdf/0705.0617},
Abstract = {http://arxiv.org/abs/0705.0617},
Key = {Chandrasekharan:2007up}
}
@article{fds303652,
Author = {Chandrasekharan, S and Mehta, AC},
Title = {Effects of the anomaly on the two-flavor QCD chiral phase
transition},
Journal = {Physical Review Letters},
Volume = {99},
Pages = {142004},
Year = {2007},
url = {http://arxiv.org/abs/0705.0617v1},
Abstract = {We use strongly coupled lattice QED with two flavors of
massless staggered fermions to model the chiral phase
transition in two-flavor massless QCD. Our model allows us
to vary the QCD anomaly and thus study its effects on the
transition. Our study confirms the widely accepted viewpoint
that the chiral phase transition is first order in the
absence of the anomaly. Turning on the anomaly weakens the
transition and turns it second order at a critical anomaly
strength. The anomaly strength at the tricritical point is
characterized using r=(Mη′-Mπ)/ρη′, where Mη′,
Mπ are the screening masses of the anomalous and regular
pions and ρη′ is the mass scale that governs the low
energy fluctuations of the anomalous symmetry. We estimate
that r∼7 in our model. This suggests that a strong anomaly
at the two-flavor QCD chiral phase transition is necessary
to wash out the first order transition.},
Doi = {10.1103/PhysRevLett.99.142004},
Key = {fds303652}
}
@article{fds349918,
Author = {Frank, J and Huffman, E and Chandrasekharan, S},
Title = {Emergence of Gauss' law in a Z2 lattice gauge
theory in 1 + 1 dimensions},
Journal = {Physics Letters, Section B: Nuclear, Elementary Particle and
High-Energy Physics},
Volume = {806},
Year = {2020},
Month = {July},
url = {http://dx.doi.org/10.1016/j.physletb.2020.135484},
Abstract = {We explore a Z2 Hamiltonian lattice gauge theory in one
spatial dimension with a coupling h, without imposing any
Gauss' law constraint. We show that in our model h=0 is a
free deconfined quantum critical point containing massless
fermions where all Gauss' law sectors are equivalent. The
coupling h is a relevant perturbation of this critical point
and fermions become massive due to confinement and chiral
symmetry breaking. To study the emergent Gauss' law sectors
at low temperatures in this massive phase we use a quantum
Monte Carlo method that samples configurations of the
partition function written in a basis in which local
conserved charges are diagonal. We find that two Gauss' law
sectors, related by particle-hole symmetry, emerge
naturally. When the system is doped with an extra particle,
many more Gauss's law sectors related by translation
invariance emerge. Using results in the range 0.01<h≤0.15
we find that three different mass scales of the model behave
like hp where p≈0.579.},
Doi = {10.1016/j.physletb.2020.135484},
Key = {fds349918}
}
@article{fds373904,
Author = {Liu, H and Huffman, E and Chandrasekharan, S and Kaul,
RK},
Title = {Erratum: Quantum Criticality of Antiferromagnetism and
Superconductivity with Relativity [Phys. Rev. Lett. 128,
117202 (2022)].},
Journal = {Physical review letters},
Volume = {131},
Number = {13},
Pages = {139901},
Year = {2023},
Month = {September},
url = {http://dx.doi.org/10.1103/physrevlett.131.139901},
Abstract = {This corrects the article DOI: 10.1103/PhysRevLett.128.117202.},
Doi = {10.1103/physrevlett.131.139901},
Key = {fds373904}
}
@article{Chandrasekharan:2004uw,
Author = {Chandrasekharan, Shailesh and Strouthos, Costas
G.},
Title = {Failure of mean field theory at large N},
Journal = {Phys. Rev. Lett.},
Volume = {94},
Pages = {061601},
Year = {2005},
url = {http://arxiv.org/pdf/hep-lat/0410036},
Abstract = {http://arxiv.org/abs/hep-lat/0410036},
Key = {Chandrasekharan:2004uw}
}
@article{fds245715,
Author = {Chandrasekharan, S and Strouthos, CG},
Title = {Failure of Mean Field Theory at Large N},
Journal = {Physical Review Letters},
Volume = {94},
Number = {6},
Pages = {061601},
Year = {2005},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/15783719},
Abstract = {We study strongly coupled lattice QCD with N colors of
staggered fermions in 3+1 dimensions. While mean field
theory describes the low temperature behavior of this theory
at large N, it fails in the scaling region close to the
finite temperature second order chiral phase transition. The
universal critical region close to the phase transition
belongs to the 3D XY universality class even when N becomes
large. This is in contrast to Gross-Neveu models where the
critical region shrinks as N (the number of flavors)
increases and mean field theory is expected to describe the
phase transition exactly in the limit of infinite N. Our
work demonstrates that infrared fluctuations can be
important close to second order phase transitions even when
N is strictly infinite.},
Doi = {10.1103/physrevlett.94.061601},
Key = {fds245715}
}
@article{fds303641,
Author = {Chandrasekharan, S},
Title = {Fermion bag approach to fermion sign problems},
Journal = {The European Physical Journal A},
Volume = {49},
Number = {7},
Pages = {90},
Publisher = {Springer Science and Business Media LLC},
Year = {2013},
Month = {July},
url = {http://arxiv.org/abs/1304.4900v1},
Abstract = {The fermion bag approach is a new method to tackle fermion
sign problems in lattice field theories. Using this approach
it is possible to solve a class of sign problems that seem
unsolvable by traditional methods. The new solutions emerge
when partition functions are written in terms of fermion
bags and bosonic worldlines. In these new variables it is
possible to identify hidden pairing mechanisms which lead to
the solutions. The new solutions allow us for the first time
to use Monte Carlo methods to solve a variety of interesting
lattice field theories, thus creating new opportunities for
understanding strongly correlated fermion
systems.},
Doi = {10.1140/epja/i2013-13090-y},
Key = {fds303641}
}
@article{fds331601,
Author = {Huffman, E and Chandrasekharan, S},
Title = {Fermion bag approach to Hamiltonian lattice field theories
in continuous time},
Journal = {Physical Review D - Particles, Fields, Gravitation and
Cosmology},
Volume = {96},
Number = {11},
Publisher = {American Physical Society},
Year = {2017},
Month = {December},
url = {http://dx.doi.org/10.1103/PhysRevD.96.114502},
Abstract = {We extend the idea of fermion bags to Hamiltonian lattice
field theories in the continuous time formulation. Using a
class of models we argue that the temperature is a parameter
that splits the fermion dynamics into small spatial regions
that can be used to identify fermion bags. Using this idea
we construct a continuous time quantum Monte Carlo algorithm
and compute critical exponents in the 3d Ising Gross-Neveu
universality class using a single flavor of massless
Hamiltonian staggered fermions. We find η=0.54(6) and
ν=0.88(2) using lattices up to N=2304 sites. We argue that
even sizes up to N=10,000 sites should be accessible with
supercomputers available today.},
Doi = {10.1103/PhysRevD.96.114502},
Key = {fds331601}
}
@article{fds245685,
Author = {Chandrasekharan, S},
Title = {Fermion bag approach to lattice field theories},
Journal = {Physical Review D},
Volume = {82},
Number = {2},
Pages = {025007},
Publisher = {American Physical Society (APS)},
Year = {2010},
ISSN = {1550-7998},
url = {http://hdl.handle.net/10161/4276 Duke open
access},
Abstract = {We propose a new approach to the fermion sign problem in
systems where there is a coupling U such that when it is
infinite the fermions are paired into bosons, and there is
no fermion permutation sign to worry about. We argue that as
U becomes finite, fermions are liberated but are naturally
confined to regions which we refer to as fermion bags. The
fermion sign problem is then confined to these bags and may
be solved using the determinantal trick. In the parameter
regime where the fermion bags are small and their typical
size does not grow with the system size, construction of
Monte Carlo methods that are far more efficient than
conventional algorithms should be possible. In the region
where the fermion bags grow with system size, the fermion
bag approach continues to provide an alternative approach to
the problem but may lose its main advantage in terms of
efficiency. The fermion bag approach also provides new
insights and solutions to sign problems. A natural solution
to the "silver blaze problem" also emerges. Using the
three-dimensional massless lattice Thirring model as an
example, we introduce the fermion bag approach and
demonstrate some of these features. We compute the critical
exponents at the quantum phase transition and find
ν=0.87(2) and η=0.62(2). © 2010 The American Physical
Society.},
Doi = {10.1103/PhysRevD.82.025007},
Key = {fds245685}
}
@article{fds245681,
Author = {Chandrasekharan, S and Li, A},
Title = {Fermion bag approach to the sign problem in strongly coupled
lattice QED with Wilson fermions},
Journal = {Journal of High Energy Physics},
Volume = {018},
Number = {1},
Publisher = {Springer Nature},
Year = {2011},
ISSN = {1126-6708},
url = {http://www.springerlink.com/content/e051x42j2xn1x087/},
Abstract = {We explore the sign problem in strongly coupled lattice QED
with one flavor of Wilson fermions in four dimensions using
the fermion bag formulation. We construct rules to compute
the weight of a fermion bag and show that even though the
fermions are confined into bosons, fermion bags with
negative weights do exist. By classifying fermion bags as
either simple or complex, we find numerical evidence that
large complex bags with positive and negative weights come
with equal probabilities. On the other hand simple bags have
a large probability of having a positive weight. In analogy
with the meron cluster approach, we suggest that eliminating
the complex bags from the partition function should
alleviate the sign problem while capturing the important
physics. We also find a modified model containing only
simple bags which does not suffer from any sign problem and
argue that it contains a parity breaking phase transition
similar to the original model. We also prove that when the
hopping parameter is strictly infinite all fermion bags are
non-negative.},
Doi = {10.1007/JHEP01(2011)018},
Key = {fds245681}
}
@article{PosLattice2012,
Author = {Chandrasekharan Shailesh},
Title = {Fermion Bag Solutions to Sign Problems},
Journal = {Proceedings of Science},
Volume = {Lattice2012},
Pages = {224},
Year = {2012},
Month = {December},
url = {http://dx.doi.org/10.22323/1.164.0224},
Abstract = {The fermion bag approach provides new solutions to sign
problems. Here we show this by using a simple example of a
lattice Yukawa model constructed with staggered fermions and
containing a Z2 chiral symmetry. We argue that in the
conventional formulation of the model the fermion
determinant is real but not necessarily positive. However,
when formulated in terms of fermion bags, the sign problem
is absent. The solution requires the fermionic part to be
formulated in terms of fermion bags, while the bosonic part
needs to be reformulated in world-line variables.},
Doi = {10.22323/1.164.0224},
Key = {PosLattice2012}
}
@article{PhysRevD.85.091502,
Author = {Chandrasekharan, S and Li, A},
Title = {Fermion bag solutions to some sign problems in four-fermion
field theories},
Journal = {Phys. Rev. D},
Volume = {85},
Number = {9},
Pages = {091502},
Publisher = {American Physical Society},
Year = {2012},
Month = {May},
ISSN = {1550-7998},
url = {http://link.aps.org/doi/10.1103/PhysRevD.85.091502},
Abstract = {Lattice four-fermion models containing N flavors of
staggered fermions, which are invariant under Z 2 and U(1)
chiral symmetries, are known to suffer from sign problems
when formulated using the auxiliary field approach. Although
these problems have been ignored in previous studies, they
can be severe. Here we show that the sign problems disappear
when the models are formulated in the fermion bag approach,
allowing us to solve them rigorously for the first time. ©
2012 American Physical Society.},
Doi = {10.1103/PhysRevD.85.091502},
Key = {PhysRevD.85.091502}
}
@article{fds303637,
Author = {Chandrasekharan, S},
Title = {Fermion bags and a new origin for a fermion
mass},
Journal = {Proceedings of Science},
Volume = {Part F130500},
Year = {2014},
Month = {January},
url = {http://arxiv.org/abs/1412.3532v1},
Abstract = {The fermion bag is a powerful idea that helps to solve
fermion lattice field theories using Monte Carlo methods.
Some sign problems that had remained unsolved earlier can be
solved within this framework. In this work we argue that the
fermion bag also gives insight into a new mechanism of
fermion mass generation, especially at strong couplings
where fermion masses are related to the fermion bag size. On
the other hand, chiral condensates arise due to zero modes
in the Dirac operator within a fermion bag. Although in
traditional four-fermion models the two quantities seem to
be related, we show that they can be decoupled. While
fermion bags become small at strong couplings, the ability
of zero modes of the Dirac operator within fermion bags to
produce a chiral condensate, can be suppressed by the
presence of additional zero modes from other fermions. Thus,
fermions can become massive even without a chiral
condensate. This new mechanism of mass generation was
discovered long ago in lattice field theory, but has
remained unappreciated. Recent work suggests that it may be
of interest even in continuum quantum field
theory.},
Key = {fds303637}
}
@article{PhysRevLett.108.140404,
Author = {Chandrasekharan, S and Li, A},
Title = {Fermion Bags, Duality, and the Three Dimensional Massless
Lattice Thirring Model},
Journal = {Phys. Rev. Lett.},
Volume = {108},
Number = {14},
Pages = {140404},
Publisher = {American Physical Society},
Year = {2012},
Month = {April},
url = {http://www.ncbi.nlm.nih.gov/pubmed/22540775},
Abstract = {The recently proposed fermion-bag approach is a powerful
technique to solve some four-fermion lattice field theories.
Because of the existence of a duality between strong and
weak couplings, the approach leads to efficient Monte Carlo
algorithms in both these limits. The new method allows us
for the first time to accurately compute quantities close to
the quantum critical point in the three dimensional lattice
Thirring model with massless fermions on large lattices. The
critical exponents at the quantum critical point are found
to be ν=0.85(1), η=0.65(1), and η(ψ)=0.37(1).},
Doi = {10.1103/PhysRevLett.108.140404},
Key = {PhysRevLett.108.140404}
}
@article{fds327863,
Author = {Chandrasekharan, S},
Title = {Fermion bags, topology and index theorems},
Journal = {Proceedings of Science},
Volume = {Part F128557},
Year = {2016},
Month = {January},
Abstract = {The fermion bag formulation helps to extend the concepts of
topology and index theorem associated with non-Abelian gauge
theories to simple lattice fermion field theories. Using
this extension we can argue that fermion masses can arise
either through the traditional mechanism where some lattice
symmetry of the action that forbids fermion mass terms is
explicitly, anomalously, or spontaneously broken, or through
a non-traditional mechanism where all lattice symmetries
continue to be preserved. We provide examples of simple
fermion lattice field theories for each of these scenarios
of fermion mass generation.},
Key = {fds327863}
}
@article{Chandrasekharan:1999vz,
Author = {Chandrasekharan Shailesh},
Title = {Fermion cluster algorithms},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {83},
Number = {1-3},
Pages = {774-776},
Year = {2000},
url = {http://arxiv.org/pdf/hep-lat/9909007},
Abstract = {http://arxiv.org/abs/hep-lat/9909007},
Doi = {10.1016/s0920-5632(00)00418-7},
Key = {Chandrasekharan:1999vz}
}
@article{fds323134,
Author = {Ayyar, V and Chandrasekharan, S},
Title = {Fermion masses through four-fermion condensates},
Journal = {Journal of High Energy Physics},
Volume = {2016},
Number = {10},
Publisher = {Springer Nature},
Year = {2016},
Month = {October},
url = {http://dx.doi.org/10.1007/JHEP10(2016)058},
Abstract = {Fermion masses can be generated through four-fermion
condensates when symmetries prevent fermion bilinear
condensates from forming. This less explored mechanism of
fermion mass generation is responsible for making four
reduced staggered lattice fermions massive at strong
couplings in a lattice model with a local four-fermion
coupling. The model has a massless fermion phase at weak
couplings and a massive fermion phase at strong couplings.
In particular there is no spontaneous symmetry breaking of
any lattice symmetries in both these phases. Recently it was
discovered that in three space-time dimensions there is a
direct second order phase transition between the two phases.
Here we study the same model in four space-time dimensions
and find results consistent with the existence of a narrow
intermediate phase with fermion bilinear condensates, that
separates the two asymptotic phases by continuous phase
transitions.},
Doi = {10.1007/JHEP10(2016)058},
Key = {fds323134}
}
@article{fds347749,
Author = {Chandrasekharan, S and Huffman, E},
Title = {Fermion-bag inspired Hamiltonian lattice field theory for
fermionic quantum criticality},
Journal = {Physical Review D: Particles, Fields, Gravitation and
Cosmology},
Volume = {07},
Number = {7},
Publisher = {American Physical Society},
Year = {2020},
Month = {April},
url = {http://dx.doi.org/10.1103/PhysRevD.101.074501},
Abstract = {Motivated by the fermion bag approach we construct a new
class of Hamiltonian lattice field theories that can help us
to study fermionic quantum critical points. As a test of our
method we construct the partition function of a simple
lattice Hamiltonian in 2+1 dimensions in discrete time, with
a temporal lattice spacing ε. When ε→0 we obtain the
partition function of the original lattice Hamiltonian. But
when ε=1 we obtain a new type of space-time lattice field
theory which treats space and time differently. Here we show
that both continuous-time and discrete-time lattice models
have a fermionic quantum critical point with critical
exponents that match within errors. The fermion bag
algorithms run relatively faster on the discrete-time model
and allow us to compute quantities even on 1003 lattices
near the quantum critical point.},
Doi = {10.1103/PhysRevD.101.074501},
Key = {fds347749}
}
@article{Chandrasekharan:1994ae,
Author = {Chandrasekharan, S.},
Title = {Fermions with a domain wall mass: Explicit Greens function
and anomaly cancellation},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {34},
Pages = {579-582},
Year = {1994},
Key = {Chandrasekharan:1994ae}
}
@article{fds245733,
Author = {Chandrasekharan, S},
Title = {FERMIONS WITH A DOMAIN WALL MASS: EXPLICIT GREENS FUNCTION
AND ANOMALY CANCELLATION},
Journal = {Nucl. Phys. B (Proc. Suppl.)},
Volume = {34},
Number = {C},
Pages = {579-582},
Publisher = {Elsevier BV},
Year = {1994},
ISSN = {0920-5632},
url = {http://dx.doi.org/10.1016/0920-5632(94)90451-0},
Abstract = {We calculate the explicit Greens function for fermions in
2+1 dimensions, with a domain wall mass. We then show a
calculation demonstrating the anomaly cancellation when such
fermions move in the background of an abelian gauge field.
© 1994.},
Doi = {10.1016/0920-5632(94)90451-0},
Key = {fds245733}
}
@article{fds342819,
Author = {Singh, H and Chandrasekharan, S},
Title = {Few-body physics on a spacetime lattice in the worldline
approach},
Journal = {Physical Review D},
Volume = {99},
Number = {7},
Year = {2019},
Month = {April},
url = {http://dx.doi.org/10.1103/PhysRevD.99.074511},
Abstract = {We formulate the physics of two species of nonrelativistic
hard-core bosons with attractive or repulsive delta function
interactions on a spacetime lattice in the worldline
approach. We show that worm algorithms can efficiently
sample the worldline configurations in any fixed
particle-number sector if the chemical potential is tuned
carefully. Since fermions can be treated as hard-core bosons
up to a permutation sign, we apply this approach to study
nonrelativistic fermions. The fermion permutation sign is an
observable in this approach and can be used to extract
energies in each particle-number sector. In one dimension,
nonrelativistic fermions can only permute across boundaries,
and so our approach does not suffer from sign problems in
many cases, unlike the auxiliary field method. Using our
approach, we discover limitations of the recently proposed
complex Langevin calculations in one spatial dimension for
some parameter regimes. In higher dimensions, our method
suffers from the usual fermion sign problem. Here we provide
evidence that it may be possible to alleviate this problem
for few-body physics.},
Doi = {10.1103/PhysRevD.99.074511},
Key = {fds342819}
}
@article{fds245686,
Author = {Banerjee, D and Chandrasekharan, S},
Title = {Finite size effects in the presence of a chemical potential:
A study in the classical non-linear O(2)
sigma-model},
Journal = {Physical Review D},
Volume = {81},
Number = {12},
Pages = {125007},
Publisher = {American Physical Society (APS)},
Year = {2010},
ISSN = {1550-7998},
url = {http://hdl.handle.net/10161/4275 Duke open
access},
Abstract = {In the presence of a chemical potential, the physics of
level crossings leads to singularities at zero temperature,
even when the spatial volume is finite. These singularities
are smoothed out at a finite temperature but leave behind
nontrivial finite size effects which must be understood in
order to extract thermodynamic quantities using Monte Carlo
methods, particularly close to critical points. We
illustrate some of these issues using the classical
nonlinear O(2) sigma model with a coupling β and chemical
potential μ on a 2+1-dimensional Euclidean lattice. In the
conventional formulation this model suffers from a sign
problem at nonzero chemical potential and hence cannot be
studied with the Wolff cluster algorithm. However, when
formulated in terms of the worldline of particles, the sign
problem is absent, and the model can be studied efficiently
with the "worm algorithm." Using this method we study the
finite size effects that arise due to the chemical potential
and develop an effective quantum mechanical approach to
capture the effects. As a side result we obtain energy
levels of up to four particles as a function of the box size
and uncover a part of the phase diagram in the (β,μ)
plane. © 2010 The American Physical Society.},
Doi = {10.1103/PhysRevD.81.125007},
Key = {fds245686}
}
@article{Chandrasekharan:2000fd,
Author = {Chandrasekharan, S. and Chudnovsky, V. and Schlittgen, B. and Wiese, U. J.},
Title = {Flop transitions in cuprate and color superconductors: From
SO(5) to SO(10) unification?},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {94},
Pages = {449-452},
Year = {2001},
url = {http://arxiv.org/pdf/hep-lat/0011054},
Abstract = {http://arxiv.org/abs/hep-lat/0011054},
Key = {Chandrasekharan:2000fd}
}
@article{fds245745,
Author = {Chandrasekharan, S and Chudnovski, V and Schlittgen, B and Wiese,
UJ},
Title = {FLOP TRANSITIONS IN CUPRATE AND COLOR SUPERCONDUTORS From
SO(5) to SO(10) unification?},
Journal = {Nucl. Phys. B (Proc. Suppl.)},
Volume = {94},
Number = {1-3},
Pages = {449},
Publisher = {Elsevier BV},
Year = {2001},
url = {http://dx.doi.org/10.1016/S0920-5632(01)01002-7},
Abstract = {The phase diagrams of cuprate superconductors and of QCD at
non-zero baryon chemical potential are qualitatively
similar. The Neel phase of the cuprates corresponds to the
chirally broken phase of QCD, and the high-temperature
superconducting phase corresponds to the color
superconducting phase. In the SO(5) theory for the cuprates
the $SO(3)_s$ spin rotational symmetry and the $U(1)_{em}$
gauge symmetry of electromagnetism are dynamically unified.
This suggests that the $SU(2)_L \otimes SU(2)_R \otimes
U(1)_B$ chiral symmetry of QCD and the $SU(3)_c$ color gauge
symmetry may get unified to SO(10). Dynamical enhancement of
symmetry from $SO(2)_s \otimes \Z(2)$ to $SO(3)_s$ is known
to occur in anisotropic antiferromagnets. In these systems
the staggered magnetization flops from an easy 3-axis into
the 12-plane at a critical value of the external magnetic
field. Similarly, the phase transitions in the SO(5) and
SO(10) models are flop transitions of a ``superspin''.
Despite this fact, a renormalization group flow analysis in
$4-\epsilon$ dimensions indicates that a point with full
SO(5) or SO(10) symmetry exists neither in the cuprates nor
in QCD.},
Doi = {10.1016/S0920-5632(01)01002-7},
Key = {fds245745}
}
@article{Chandrasekharan:2007sch,
Author = {Jiang, F.-J. and Nyfeler, M. and Chandrasekharan, S. and Wiese, U. -J.},
Title = {From an Antiferromagnet to a Valence Bond Solid: Evidence
for a First Order Phase Transition},
Journal = {J. of Stat. Mech},
Volume = {P02009},
Year = {2008},
Key = {Chandrasekharan:2007sch}
}
@article{fds245707,
Author = {Jiang, FJ and Nyfeler, M and Chandrasekharan, S and Wiese,
UJ},
Title = {From an Antiferromagnet to a Valence Bond Solid: Evidence
for a First Order Phase Transition},
Journal = {J. Stat. Mech.},
Volume = {2008},
Number = {2},
Pages = {P02009},
Publisher = {IOP Publishing},
Year = {2008},
ISSN = {1742-5468},
url = {http://iopscience.iop.org/1742-5468/2008/02/P02009/},
Abstract = {Using a loop-cluster algorithm we investigate the spin 1/2
Heisenberg antiferromagnet on a square lattice with exchange
coupling $J$ and an additional four-spin interaction of
strength $Q$. We confirm the existence of a phase transition
separating antiferromagnetism at $J/Q > J_c/Q$ from a
valence bond solid (VBS) state at $J/Q J_c/Q$ the staggered
magnetization, the spin stiffness, and the spinwave velocity
of the antiferromagnet are determined by fitting Monte Carlo
data to analytic results from the systematic low-energy
effective field theory for magnons. Finally, we also
investigate the physics of the VBS state at
$J/Q},
Doi = {10.1088/1742-5468/2008/02/P02009},
Key = {fds245707}
}
@article{Chandrasekharan:2001ya,
Author = {Chandrasekharan, S. and Scarlet, B. and Wiese, U.
J.},
Title = {From spin ladders to the 2-d O(3) model at non-zero
density},
Journal = {Comput. Phys. Commun.},
Volume = {147},
Pages = {388-393},
Year = {2002},
url = {http://arxiv.org/pdf/hep-lat/0110215},
Abstract = {http://arxiv.org/abs/hep-lat/0110215},
Key = {Chandrasekharan:2001ya}
}
@article{fds245747,
Author = {Chandrasekharan, S and Scarlet, B and Wiese, UJ},
Title = {FROM SPIN LADDERS TO THE 2-D O(3) MODEL AT NONZERO
DENSITY},
Journal = {Comput. Phys. Commun.},
Volume = {147},
Number = {1-2},
Pages = {388},
Publisher = {Elsevier BV},
Year = {2002},
url = {http://dx.doi.org/10.1016/S0010-4655(02)00311-9},
Abstract = {The numerical simulation of various field theories at
non-zero chemical potential suffers from severe complex
action problems. In particular, QCD at non-zero quark
density can presently not be simulated for that reason. A
similar complex action problem arises in the 2-d O(3) model
-- a toy model for QCD. Here we construct the 2-d O(3) model
at non-zero density via dimensional reduction of an
antiferromagnetic quantum spin ladder in a magnetic field.
The complex action problem of the 2-d O(3) model manifests
itself as a sign problem of the ladder system. This sign
problem is solved completely with a meron-cluster
algorithm.},
Doi = {10.1016/S0010-4655(02)00311-9},
Key = {fds245747}
}
@article{fds336441,
Author = {Ayyar, V and Chandrasekharan, S},
Title = {Generating a mass gap using Feynman diagrams in an
asymptotically free theory},
Journal = {EPJ Web of Conferences},
Volume = {175},
Pages = {11010-11010},
Publisher = {E D P SCIENCES},
Editor = {Della Morte and M and Fritzsch, P and Gámiz Sánchez and E and Pena Ruano,
C},
Year = {2018},
Month = {March},
url = {http://dx.doi.org/10.1051/epjconf/201817511010},
Abstract = {Using the example of a two dimensional four-fermion lattice
field theory, we show that Feynman diagrams can generate a
mass gap in a theory with massless fermions that interact
via a marginally relevant coupling. We show this by
introducing an infrared cutoff that makes the perturbation
series for the partition function convergent. We use a Monte
Carlo approach to sample sufficiently high orders of
diagrams and thus expose the presence of the mass
gap.},
Doi = {10.1051/epjconf/201817511010},
Key = {fds336441}
}
@article{fds331600,
Author = {Chandrasekharan, S and Ayyar, V},
Title = {Generating a nonperturbative mass gap using Feynman diagrams
in an asymptotically free theory},
Journal = {Physical Review D - Particles, Fields, Gravitation and
Cosmology},
Volume = {96},
Number = {11},
Publisher = {American Physical Society},
Year = {2017},
Month = {December},
url = {http://dx.doi.org/10.1103/PhysRevD.96.114506},
Abstract = {Using the example of a two-dimensional four-fermion lattice
field theory we demonstrate that Feynman diagrams can
generate a mass gap when massless fermions interact via a
marginally relevant coupling. We introduce an infrared
cutoff through the finite system size so that the
perturbation series for the partition function and
observables become convergent. We then use the Monte Carlo
approach to sample sufficiently high orders of diagrams to
expose the presence of a mass gap in the lattice
model.},
Doi = {10.1103/PhysRevD.96.114506},
Key = {fds331600}
}
@article{Chandrasekharan:1998em,
Author = {Chandrasekharan, S},
Title = {Ginsparg-Wilson fermions: A study in the Schwinger
model},
Journal = {Physical Review D - Particles, Fields, Gravitation and
Cosmology},
Volume = {59},
Number = {9},
Pages = {1-8},
Year = {1999},
url = {http://arxiv.org/pdf/hep-lat/9810007},
Abstract = {The qualitative features of Ginsparg-Wilson fermions, as
formulated by Neuberger, coupled to two-dimensional U(1)
gauge theory are studied. The role of the Wilson mass
parameter in changing the number of massless flavors in the
theory and its connection with the index of the Dirac
operator is studied. Although the index of the Dirac
operator is not related to the geometric definition of the
topological charge for strong couplings, the two start to
agree as soon as one goes to moderately weak couplings. This
produces the desired singularity in the quenched chiral
condensate which appears to be very difficult to reproduce
with staggered fermions. The fermion determinant removes the
singularity and reproduces the known chiral condensate and
the meson mass within understandable errors. ©1999 The
American Physical Society.},
Key = {Chandrasekharan:1998em}
}
@article{fds303655,
Author = {Chandrasekharan, S},
Title = {GINSPARG-WILSON FERMIONS: A STUDY IN THE SCHWINGER
MODEL},
Journal = {Phys. Rev. D},
Volume = {59},
Number = {9},
Pages = {094502},
Publisher = {American Physical Society (APS)},
Year = {1999},
url = {http://arxiv.org/abs/hep-lat/9810007v2},
Abstract = {Qualitative features of Ginsparg-Wilson fermions, as
formulated by Neuberger, coupled to two dimensional U(1)
gauge theory are studied. The role of the Wilson mass
parameter in changing the number of massless flavors in the
theory and its connection with the index of the Dirac
operator is studied. Although the index of the Dirac
operator is not related to the geometric definition of the
topological charge for strong couplings, the two start to
agree as soon as one goes to moderately weak couplings. This
produces the desired singularity in the quenched chiral
condensate which appears to be very difficult to reproduce
with staggered fermions. The fermion determinant removes the
singularity and reproduces the known chiral condensate and
the meson mass within understandable errors.},
Doi = {10.1103/PhysRevD.59.094502},
Key = {fds303655}
}
@article{Brower:1998kg,
Author = {Brower, R. and Chandrasekharan, S. and Wiese, U.
J.},
Title = {Green's functions from quantum cluster algorithms},
Journal = {Physica A},
Volume = {261},
Pages = {520},
Year = {1998},
url = {http://arxiv.org/pdf/cond-mat/9801003},
Abstract = {http://arxiv.org/abs/cond-mat/9801003},
Key = {Brower:1998kg}
}
@article{fds245737,
Author = {Brower, R and Chandrasekharan, S and Wiese, UJ},
Title = {GREEN'S FUNCTIONS FROM QUANTUM CLUSTER ALGORITHMS},
Journal = {Physica A},
Volume = {261},
Number = {3-4},
Pages = {520-533},
Publisher = {Elsevier BV},
Year = {1998},
url = {http://dx.doi.org/10.1016/S0378-4371(98)00325-2},
Abstract = {We show that cluster algorithms for quantum models have a
meaning independent of the basis chosen to construct them.
Using this idea, we propose a new method for measuring with
little effort a whole class of Green's functions, once a
cluster algorithm for the partition function has been
constructed. To explain the idea, we consider the quantum XY
model and compute its two point Green's function in various
ways, showing that all of them are equivalent. We also
provide numerical evidence confirming the analytic
arguments. Similar techniques are applicable to other
models. In particular, in the recently constructed quantum
link models, the new technique allows us to construct
improved estimators for Wilson loops and may lead to a very
precise determination of the glueball spectrum.},
Doi = {10.1016/S0378-4371(98)00325-2},
Key = {fds245737}
}
@article{fds245666,
Author = {Brower, R and Chandrasekharan, S and Wiese, U-J},
Title = {Green’s functions from quantum cluster algorithms11This
work is supported in part by funds provided by the US
Department of Energy (DOE) under cooperative research
agreement DE-FC02-94ER40818.},
Volume = {261},
Number = {3},
Pages = {520-533},
Year = {1998},
Abstract = {We show that cluster algorithms for quantum models have a
meaning independent of the basis chosen to construct them.
Using this idea, we propose a new method for measuring with
little effort a whole class of Green’s functions, once a
cluster algorithm for the partition function has been
constructed. To explain the idea, we consider the quantum XY
model and compute its two point Green’s function in
various ways, showing that all of them are equivalent. We
also provide numerical evidence confirming the analytic
arguments. Similar techniques are applicable to other
models. In particular, in the recently constructed quantum
link models, the new technique allows us to construct
improved estimators for Wilson loops and may lead to a very
precise determination of the glueball spectrum.},
Key = {fds245666}
}
@article{fds245704,
Author = {Kaul, RK and Ullmo, D and Zarand, G and Chandrasekharan, S and Baranger,
HU},
Title = {Ground state and excitations of quantum dots with magnetic
impurities},
Journal = {Phys. Rev. B},
Volume = {80},
Number = {3},
Pages = {035318},
Publisher = {American Physical Society (APS)},
Year = {2009},
ISSN = {1098-0121},
url = {http://link.aps.org/abstract/PRB/v80/e035318},
Abstract = {We consider an “impurity” with a spin degree of freedom
coupled to a finite reservoir of non-interacting electrons,
a system which may be realized by either a true impurity in
a metallic nano-particle or a small quantum dot coupled to a
large one. We show how the physics of such a spin impurity
is revealed in the many-body spectrum of the entire
finite-size system; in particular, the evolution of the
spectrum with the strength of the impurity-reservoir
coupling reflects the fundamental many-body correlations
present. Explicit calculation in the strong and weak
coupling limits shows that the spectrum and its evolution
are sensitive to the nature of the impurity and the parity
of electrons in the reservoir. The effect of the finite size
spectrum on two experimental observables is considered.
First, we propose an experimental setup in which the
spectrum may be conveniently measured using tunneling
spectroscopy. A rate equation calculation of the
differential conductance suggests how the many-body spectral
features may be observed. Second, the finite-temperature
magnetic susceptibility is presented, both the impurity
susceptibility and the local susceptibility. Extensive
quantum Monte-Carlo calculations show that the local
susceptibility deviates from its bulk scaling form.
Nevertheless, for special assumptions about the reservoir
– the “clean Kondo box” model – we demonstrate that
finite-size scaling is recovered. Explicit numerical
evaluations of these scaling functions are given, both for
even and odd parity and for the canonical and
grand-canonical ensembles.},
Doi = {10.1103/PhysRevB.80.035318},
Key = {fds245704}
}
@article{fds355953,
Author = {Liu, H and Chandrasekharan, S and Kaul, R},
Title = {Hamiltonian models of lattice fermions solvable by the
meron-cluster algorithm},
Journal = {Physical Review D: Particles, Fields, Gravitation and
Cosmology},
Volume = {103},
Number = {5},
Publisher = {American Physical Society},
Year = {2020},
Month = {November},
url = {http://dx.doi.org/10.1103/PhysRevD.103.054033},
Abstract = {We introduce a half-filled Hamiltonian of spin-half lattice
fermions that can be studied with the efficient
meron-cluster algorithm in any dimension. As with the usual
bipartite half-filled Hubbard models, the naïve U(2)
symmetry is enhanced to SO(4). On the other hand our model
has a novel spin-charge flip ℤC2 symmetry which is an
important ingredient of free massless fermions. In this work
we focus on one spatial dimension, and show that our model
can be viewed as a lattice-regularized two-flavor
chiral-mass Gross-Neveu model. Our model remains solvable in
the presence of the Hubbard coupling U, which maps to a
combination of Gross-Neveu and Thirring couplings in one
dimension. Using the meron-cluster algorithm we find that
the ground state of our model is a valence bond solid when
U=0. From our field theory analysis, we argue that the
valence bond solid forms inevitably because of an
interesting frustration between spin and charge sectors in
the renormalization group flow enforced by the ℤC2
symmetry. This state spontaneously breaks translation
symmetry by one lattice unit, which can be identified with a
ℤχ2 chiral symmetry in the continuum. We show that
increasing U induces a quantum phase transition to a
critical phase described by the SU(2)1 Wess-Zumino-Witten
theory. The quantum critical point between these two phases
is known to exhibit a novel symmetry enhancement between
spin and dimer. Here we verify the scaling relations of
these correlation functions near the critical point
numerically. Our study opens up the exciting possibility of
numerical access to similar novel phase transitions in
higher dimensions in fermionic lattice models using the
meron-cluster algorithm.},
Doi = {10.1103/PhysRevD.103.054033},
Key = {fds355953}
}
@article{fds353933,
Author = {H. Liu and S. Chandrasekharan and R. Kaul},
Title = {Hamiltonian models of lattice fermions solvable by the
meron-cluster algorithm},
Journal = {Physical Review D},
Year = {2020},
Month = {November},
url = {https://arxiv.org/abs/2011.13208},
Abstract = {https://arxiv.org/abs/2011.13208},
Key = {fds353933}
}
@article{PhysRevB.66.045113,
Author = {Chandrasekharan, S and Osborn, JC},
Title = {Kosterlitz-Thouless universality in a fermionic
system},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {66},
Number = {4},
Pages = {451131-451135},
Year = {2002},
ISSN = {0163-1829},
Abstract = {An extension of the attractive Hubbard model is constructed
to study the critical behavior near a finite-temperature
superconducting phase transition in two dimensions using the
recently developed meron-cluster algorithm. Unlike previous
calculations in the attractive Hubbard model which were
limited to small lattices, the algorithm is used to study
the critical behavior on lattices as large as 128 × 128.
These precise results show that a fermionic system can
undergo a finite temperature phase transition whose critical
behavior is well described by the predictions of Kosterlitz
and Thouless almost three decades ago. In particular it is
confirmed that the spatial winding number susceptibility
obeys the well known predictions of finite size scaling for
T <Tc and up to logarithmic corrections the pair
susceptibility scales as L2-η at large volumes with 0 ≤
η ≤ 0.25 for 0 ≤T≤T.},
Key = {PhysRevB.66.045113}
}
@article{fds303656,
Author = {Chandrasekharan, S and Osborn, JC},
Title = {KOSTERLITZ-THOULESS UNIVERSALITY IN A FERMIONIC
SYSTEM},
Journal = {Physical Review B},
Volume = {66},
Number = {4},
Pages = {045113},
Publisher = {American Physical Society (APS)},
Year = {2002},
url = {http://arxiv.org/abs/cond-mat/0109424v1},
Abstract = {A new extension of the attractive Hubbard model is
constructed to study the critical behavior near a finite
temperature superconducting phase transition in two
dimensions using the recently developed meron-cluster
algorithm. Unlike previous calculations in the attractive
Hubbard model which were limited to small lattices, the new
algorithm is used to study the critical behavior on lattices
as large as $128\times 128$. These precise results for the
first time show that a fermionic system can undergo a finite
temperature phase transition whose critical behavior is well
described by the predictions of Kosterlitz and Thouless
almost three decades ago. In particular it is confirmed that
the spatial winding number susceptibility obeys the well
known predictions of finite size scaling for
$T},
Doi = {10.1103/PhysRevB.66.045113},
Key = {fds303656}
}
@article{Chandrasekharan:2003qv,
Author = {Chandrasekharan, Shailesh and Strouthos, Costas
G.},
Title = {Kosterlitz-Thouless universality in dimer
models},
Journal = {Phys. Rev. D},
Volume = {68},
Pages = {091502},
Year = {2003},
url = {http://arxiv.org/pdf/hep-lat/0306034},
Abstract = {http://arxiv.org/abs/hep-lat/0306034},
Key = {Chandrasekharan:2003qv}
}
@article{fds245718,
Author = {Chandrasekharan, S and Strouthos, C},
Title = {KOSTERLITZ-THOULESS UNIVERSALITY IN DIMER
MODELS},
Journal = {Physical Reviews D (Rapid Communications)
arXiv:hep-lat/0306034},
Volume = {68},
Number = {9},
Pages = {091502},
Publisher = {American Physical Society (APS)},
Year = {2003},
ISSN = {0556-2821},
url = {http://dx.doi.org/10.1103/PhysRevD.68.091502},
Abstract = {Using the monomer-dimer representation of strongly coupled
U(N) lattice gauge theories with staggered fermions, we
study finite temperature chiral phase transitions in 2+1
dimensions. A new cluster algorithm allows us to compute
monomer-monomer and dimer-dimer correlations at zero monomer
density (chiral limit) accurately on large lattices. This
makes it possible to show convincingly, for the first time,
that these models undergo a finite temperature phase
transition which belongs to the Kosterlitz-Thouless
universality class. We find that the phase transition
persists for all values of N, but occurs at different values
of the critical temperature Tc. Further, when T /Tc is held
fixed, the mean field analysis often used in the large N
limit breaks down. © The American Physical
Society.},
Doi = {10.1103/PhysRevD.68.091502},
Key = {fds245718}
}
@article{fds245723,
Author = {Brower, R and Chandrasekharan, S and Negele, JW and Wiese,
UJ},
Title = {LATTICE QCD AT FIXED TOPOLOGY},
Journal = {Phys. Lett. B},
Volume = {560},
Pages = {64-74},
Year = {2003},
Abstract = {Since present Monte Carlo algorithms for lattice QCD may
become trapped in a fixed topological charge sector, it is
important to understand the effect of calculating at fixed
topology. In this work, we show that although the
restriction to a fixed topological sector becomes irrelevant
in the infinite volume limit, it gives rise to
characteristic finite size effects due to contributions from
all $\theta$-vacua. We calculate these effects and show how
to extract physical results from numerical data obtained at
fixed topology.},
Key = {fds245723}
}
@article{fds245673,
Author = {Chandrasekharan, S},
Title = {Lattice QCD with Ginsparg-Wilson fermions},
Journal = {Physical Review D - Particles, Fields, Gravitation and
Cosmology},
Volume = {60},
Number = {7},
Pages = {1-6},
Year = {1999},
url = {http://arxiv.org/abs/hep-lat/9805015v3},
Abstract = {Lattice QCD using fermions whose Dirac operator obeys the
Ginsparg-Wilson relation is perhaps the best known
formulation of QCD with a finite cutoff. It reproduces all
the low energy QCD phenomenology associated with chiral
symmetry at finite lattice spacings. In particular it
explains the origin of massless pions due to spontaneous
chiral symmetry breaking and leads to new ways to approach
the U(1) problem on the lattice. Here we show these results
in the path integral formulation and derive for the first
time in lattice QCD a known formal continuum relation
between the chiral condensate and the topological
susceptibility. This relation leads to predictions for the
critical behavior of the topological susceptibility near the
phase transition and can now be checked in Monte Carlo
simulations even at finite lattice spacings. ©1999 The
American Physical Society.},
Doi = {10.1103/PhysRevD.60.074503},
Key = {fds245673}
}
@article{Chandrasekharan:1998wg,
Author = {Chandrasekharan, S},
Title = {LATTICE QCD WITH GINSPARG-WILSON FERMIONS},
Journal = {Phys. Rev. D},
Volume = {60},
Number = {7},
Pages = {074503},
Year = {1999},
url = {http://arxiv.org/pdf/hep-lat/9805015},
Abstract = {Lattice QCD using fermions whose Dirac operator obeys the
Ginsparg-Wilson relation, is perhaps the best known
formulation of QCD with a finite cutoff. It reproduces all
the low energy QCD phenomenology associated with chiral
symmetry at finite lattice spacings. In particular it
explains the origin of massless pions due to spontaneous
chiral symmetry breaking and leads to new ways to approach
the U(1) problem on the lattice. Here we show these results
in the path integral formulation and derive for the first
time in lattice QCD a known formal continuum relation
between the chiral condensate and the topological
susceptibility. This relation leads to predictions for the
critical behavior of the topological susceptibility near the
phase transition and can now be checked in Monte-Carlo
simulations even at finite lattice spacings.},
Doi = {10.1103/PhysRevD.60.074503},
Key = {Chandrasekharan:1998wg}
}
@article{Chandrasekharan:2003ub,
Author = {Chandrasekharan, S and Pepe, M and Steffen, FD and Wiese,
UJ},
Title = {Lattice theories with nonlinearly realized chiral
symmetry},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {129},
Pages = {507-509},
Publisher = {Elsevier BV},
Year = {2004},
url = {http://arxiv.org/pdf/hep-lat/0309093},
Abstract = {http://arxiv.org/abs/hep-lat/0309093},
Doi = {10.1016/S0920-5632(03)02624-0},
Key = {Chandrasekharan:2003ub}
}
@article{fds245667,
Author = {Ayyar, V and Chandrasekharan, S},
Title = {Massive fermions without fermion bilinear
condensates},
Journal = {Physical Review D - Particles, Fields, Gravitation and
Cosmology},
Volume = {91},
Number = {6},
Publisher = {American Physical Society (APS)},
Year = {2015},
Month = {March},
ISSN = {1550-7998},
url = {http://dx.doi.org/10.1103/PhysRevD.91.065035},
Abstract = {We study a lattice field theory model containing two flavors
of massless staggered fermions with an onsite four-fermion
interaction. The model contains an SU(4) symmetry which
forbids nonzero fermion bilinear mass terms, due to which
there is a massless fermion phase at weak couplings.
However, even at strong couplings fermion bilinear
condensates do not appear in our model, although fermions do
become massive. While the existence of this exotic strongly
coupled massive fermion phase was established long ago, the
nature of the transition between the massless and the
massive phase has remained unclear. Using Monte Carlo
calculations in three space-time dimensions, we find
evidence for a direct second-order transition between the
two phases suggesting that the exotic lattice phase may have
a continuum limit at least in three dimensions. A similar
exotic second-order critical point was found recently in a
bilayer system on a honeycomb lattice.},
Doi = {10.1103/PhysRevD.91.065035},
Key = {fds245667}
}
@article{fds225571,
Author = {V. Ayyar and S. Chandrasekharan},
Title = {Massive fermions without fermion bilinear
condensates},
Journal = {arXiv:1410.6474 (submitted to Phys. Rev.
D)},
Year = {2014},
Month = {October},
url = {http://arxiv.org/abs/arXiv:1410.6474},
Abstract = {http://arxiv.org/abs/arXiv:1410.6474},
Key = {fds225571}
}
@article{fds245721,
Author = {Chandrasekharan, S and Cox, J and Osborn, JC and Wiese,
UJ},
Title = {MERON CLUSTER APPROACH TO SYSTEMS OF STRONGLY CORRELATED
ELECTRONS},
Journal = {Nucl. Phys. B},
Volume = {673},
Number = {3},
Pages = {405-436},
Publisher = {Elsevier BV},
Year = {2003},
url = {http://dx.doi.org/10.1016/j.nuclphysb.2003.08.041},
Abstract = {Numerical simulations of strongly correlated electron
systems suffer from the notorious fermion sign problem which
has prevented progress in understanding if systems like the
Hubbard model display high-temperature superconductivity.
Here we show how the fermion sign problem can be solved
completely with meron-cluster methods in a large class of
models of strongly correlated electron systems, some of
which are in the extended Hubbard model family and show
s-wave superconductivity. In these models we also find that
on-site repulsion can even coexist with a weak chemical
potential without introducing sign problems. We argue that
since these models can be simulated efficiently using
cluster algorithms they are ideal for studying many of the
interesting phenomena in strongly correlated electron
systems.},
Doi = {10.1016/j.nuclphysb.2003.08.041},
Key = {fds245721}
}
@article{fds245740,
Author = {Chandrasekharan, S and Cox, J and Holland, K and Wiese,
UJ},
Title = {MERON CLUSTER SIMULATION OF A CHIRAL PHASE TRANSITION WITH
STAGGERED FERMIONS.},
Journal = {Nucl. Phys. B},
Volume = {576},
Number = {1-3},
Pages = {481-500},
Publisher = {Elsevier BV},
Year = {2000},
url = {http://dx.doi.org/10.1016/S0550-3213(00)00087-0},
Abstract = {We examine a (3 + 1)-dimensional model of staggered lattice
fermions with a four-fermion interaction and ℤ(2) chiral
symmetry using the Hamiltonian formulation. This model
cannot be simulated with standard fermion algorithms because
those suffer from a very severe sign problem. We use a new
fermion simulation technique - the meron-cluster algorithm -
which solves the sign problem and leads to high-precision
numerical data. We investigate the finite temperature chiral
phase transition and verify that it is in the universality
class of the 3-d Ising model using finite-size scaling. ©
2000 Elsevier Science B.V. All rights reserved.},
Doi = {10.1016/S0550-3213(00)00087-0},
Key = {fds245740}
}
@article{fds4139,
Author = {S. Chandrasekharan and B. Scarlet and U.-J.
Wiese},
Title = {MERON CLUSTER SIMULATION OF QUANTUM SPIN LADDERS IN A
MAGNETIC FIELD},
Year = {1999},
Key = {fds4139}
}
@article{fds245741,
Author = {Chandrasekharan, S and Wiese, UJ},
Title = {MERON CLUSTER SOLUTION OF A FERMION SIGN
PROBLEM},
Journal = {Phys. Rev. Letts.},
Volume = {86},
Number = {15},
Pages = {3116-3119},
Publisher = {American Physical Society (APS)},
Year = {1999},
Month = {January},
url = {http://dx.doi.org/10.1103/PhysRevLett.83.3116},
Abstract = {We present a general strategy to solve the notorious fermion
sign problem using cluster algorithms. The method applies to
various systems in the Hubbard model family as well as to
relativistic fermions. Here it is illustrated for
non-relativistic lattice fermions. A configuration of
fermion world-lines is decomposed into clusters that
contribute independently to the fermion permutation sign. A
cluster whose flip changes the sign is referred to as a
meron. Configurations containing meron-clusters contribute 0
to the path integral, while all other configurations
contribute 1. The cluster representation describes the
partition function as a gas of clusters in the zero-meron
sector.},
Doi = {10.1103/PhysRevLett.83.3116},
Key = {fds245741}
}
@article{Chandrasekharan:2002vk,
Author = {Chandrasekharan, S. and Cox, J. and Osborn, J. C. and Wiese,
U. J.},
Title = {Meron-Cluster Approach to Systems of Strongly Correlated
Electrons},
Journal = {Nucl. Phys. B},
Volume = {673},
Pages = {405-436},
Year = {2003},
url = {http://arxiv.org/pdf/cond-mat/0201360},
Abstract = {http://arxiv.org/abs/cond-mat/0201360},
Key = {Chandrasekharan:2002vk}
}
@article{Chandrasekharan:1999ys,
Author = {Chandrasekharan, S. and Cox, J. and Holland, K. and Wiese,
U. J.},
Title = {Meron-cluster simulation of a chiral phase transition with
staggered fermions},
Journal = {Nucl. Phys. B},
Volume = {576},
Pages = {481-500},
Year = {2000},
url = {http://arxiv.org/pdf/hep-lat/9906021},
Abstract = {http://arxiv.org/abs/hep-lat/9906021},
Key = {Chandrasekharan:1999ys}
}
@article{fds303642,
Author = {Chandrasekharan, S and Scarlet, B and Wiese, U-J},
Title = {Meron-Cluster Simulation of Quantum Spin Ladders in a
Magnetic Field},
Year = {1999},
Month = {September},
url = {http://arxiv.org/abs/cond-mat/9909451v1},
Abstract = {Numerical simulations of numerous quantum systems suffer
from the notorious sign problem. Meron-cluster algorithms
lead to an efficient solution of sign problems for both
fermionic and bosonic models. Here we apply the meron
concept to quantum spin systems in an arbitrary external
magnetic field, in which case standard cluster algorithms
fail. As an example, we simulate antiferromagnetic quantum
spin ladders in a uniform external magnetic field that
competes with the spin-spin interaction. The numerical
results are in agreement with analytic predictions for the
magnetization as a function of the external
field.},
Key = {fds303642}
}
@article{Chandrasekharan:1999zt,
Author = {Chandrasekharan, S. and Scarlet, B. and Wiese, U.
J.},
Title = {Meron-Cluster Simulation of Quantum Spin Ladders in a
Magnetic Field},
Year = {1999},
url = {http://arxiv.org/pdf/cond-mat/9909451},
Abstract = {http://arxiv.org/abs/cond-mat/9909451},
Key = {Chandrasekharan:1999zt}
}
@article{Chandrasekharan:1999cm,
Author = {Chandrasekharan, Shailesh and Wiese, Uwe-Jens},
Title = {Meron-cluster solution of a fermion sign
problem},
Journal = {Phys. Rev. Lett.},
Volume = {83},
Pages = {3116-3119},
Year = {1999},
url = {http://arxiv.org/pdf/cond-mat/9902128},
Abstract = {http://arxiv.org/abs/cond-mat/9902128},
Key = {Chandrasekharan:1999cm}
}
@article{Kaul04_mesokondo,
Author = {Kaul, RK and Ullmo, D and Chandrasekharan, S and Baranger,
HU},
Title = {Mesoscopic Kondo Problem},
Journal = {Europhys. Lett.},
Volume = {71},
Number = {6},
Pages = {973},
Publisher = {cond-mat/0409211},
Year = {2005},
url = {http://www.phy.duke.edu/research/cmtheory/bg/paper/kaulucb04_mesokondo.pdf},
Abstract = {We study the effect of mesoscopic fluctuations on a magnetic
impurity coupled to a spatially confined electron gas with a
temperature in the mesoscopic range (i.e. between the mean
level spacing Δ and the Thouless energy ETh). Comparing
"poor-man's scaling" with exact Quantum Monte Carlo, we find
that for temperatures larger than the Kondo temperature,
many aspects of the fluctuations can be captured by the
perturbative technique. Using this technique in conjunction
with semi-classical approximations, we are able to calculate
the mesoscopic fluctuations for a wide variety of systems.
For temperatures smaller than the Kondo temperature, we find
large fluctuations and deviations from the universal
behavior. © EDP Sciences.},
Doi = {10.1209/epl/i2005-10184-1},
Key = {Kaul04_mesokondo}
}
@article{Cecile:2007dv,
Author = {Cecile, D. J. and Chandrasekharan, Shailesh},
Title = {Modeling pion physics in the $\epsilon$-regime of two-
flavor QCD using strong coupling lattice
QED},
Journal = {Phys. Rev.},
Volume = {D77},
Pages = {014506},
Year = {2008},
url = {http://arxiv.org/pdf/arXiv:0708.0558 [hep-lat]},
Abstract = {http://arxiv.org/abs/arXiv:0708.0558 [hep-lat]},
Key = {Cecile:2007dv}
}
@article{fds245709,
Author = {Cecile, DJ and Chandrasekharan, S},
Title = {Modeling pion physics in the epsilon-regime of two-flavor
QCD using strong coupling lattice QED},
Journal = {Phys. Rev. D},
Volume = {77},
Number = {1},
Pages = {014506},
Publisher = {American Physical Society (APS)},
Year = {2007},
ISSN = {1550-7998},
url = {http://link.aps.org/abstract/PRD/v77/e014506},
Abstract = {In order to model pions of two-flavor QCD we consider a
lattice field theory involving two flavors of staggered
quarks interacting strongly with U(1) gauge fields. For
massless quarks, this theory has an $SU_L(2)\times SU_R(2)
\times U_A(1)$ symmetry. By adding a four-fermion term we
can break the U_A(1) symmetry and thus incorporate the
physics of the QCD anomaly. We can also tune the pion decay
constant F, to be small compared to the lattice cutoff by
starting with an extra fictitious dimension, thus allowing
us to model low energy pion physics in a setting similar to
lattice QCD from first principles. However, unlike lattice
QCD, a major advantage of our model is that we can easily
design efficient algorithms to compute a variety of
quantities in the chiral limit. Here we show that the model
reproduces the predictions of chiral perturbation theory in
the $\epsilon$-regime.},
Doi = {10.1103/PhysRevD.77.014506},
Key = {fds245709}
}
@article{Chandrasekharan:2006iw,
Author = {Chandrasekharan, S},
Title = {New approaches to strong coupling lattice
QCD},
Journal = {Int. J. Mod. Phys.},
Volume = {B20},
Pages = {2714-2723},
Year = {2006},
Key = {Chandrasekharan:2006iw}
}
@article{fds303653,
Author = {Chandrasekharan, S and Pepe, M and Steffen, FD and Wiese,
UJ},
Title = {NON-LINEAR REALIZATION OF CHIRAL SYMMETRY ON THE
LATTICE},
Journal = {JHEP},
Volume = {0312},
Number = {12},
Pages = {035},
Publisher = {Springer Nature},
Year = {2003},
url = {http://arxiv.org/abs/hep-lat/0306020v2},
Abstract = {We formulate lattice theories in which chiral symmetry is
realized nonlinearly on the fermion fields. In this
framework the fermion mass term does not break chiral
symmetry. This property allows us to use the Wilson term to
remove the doubler fermions while maintaining exact chiral
symmetry on the lattice. Our lattice formulation enables us
to address non-perturbative questions in effective field
theories of baryons interacting with pions and in models
involving constituent quarks interacting with pions and
gluons. We show that a system containing a non-zero density
of static baryons interacting with pions can be studied on
the lattice without encountering complex action problems. In
our formulation one can also decide non-perturbatively if
the chiral quark model of Georgi and Manohar provides an
appropriate low-energy description of QCD. If so, one could
understand why the non-relativistic quark model works. ©
SISSA/ISAS 2004.},
Doi = {10.1088/1126-6708/2003/12/035},
Key = {fds303653}
}
@article{Bhattacharya:1999uq,
Author = {Bhattacharya, Tanmoy and Chandrasekharan, Shailesh and Gupta, Rajan and Lee, Weon-Jong and Sharpe, Stephen
R.},
Title = {Non-perturbative renormalization constants using Ward
identities},
Journal = {Phys. Lett. B},
Volume = {461},
Pages = {79-88},
Year = {1999},
url = {http://arxiv.org/pdf/hep-lat/9904011},
Abstract = {http://arxiv.org/abs/hep-lat/9904011},
Key = {Bhattacharya:1999uq}
}
@article{Bhattacharya:1998ue,
Author = {Bhattacharya, T and Chandrasekharan, S and Gupta, R and Lee, W-J and Sharpe, SR},
Title = {Non-perturbative renormalization constants using Ward
identities},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {73},
Number = {1-3},
Pages = {276-278},
Publisher = {Elsevier BV},
Year = {1999},
url = {http://arxiv.org/pdf/hep-lat/9810018},
Abstract = {http://arxiv.org/abs/hep-lat/9810018},
Doi = {10.1016/S0920-5632(99)85046-4},
Key = {Bhattacharya:1998ue}
}
@article{Chandrasekharan:2003wy,
Author = {Chandrasekharan, S. and Pepe, M. and Steffen, F. D. and Wiese, U. J.},
Title = {Nonlinear realization of chiral symmetry on the
lattice},
Journal = {JHEP},
Volume = {12},
Pages = {035},
Year = {2003},
url = {http://arxiv.org/pdf/hep-lat/0306020},
Abstract = {http://arxiv.org/abs/hep-lat/0306020},
Key = {Chandrasekharan:2003wy}
}
@article{fds245676,
Author = {Chandrasekharan, S and Pepe, M and Steffen, FD and Wiese,
U-J},
Title = {Nonlinear realization of chiral symmetry on the
lattice},
Journal = {Journal of High Energy Physics},
Volume = {7},
Number = {12},
Pages = {831-863},
Year = {2003},
ISSN = {1029-8479},
Abstract = {We formulate lattice theories in which chiral symmetry is
realized nonlinearly on the fermion fields. In this
framework the fermion mass term does not break chiral
symmetry. This property allows us to use the Wilson term to
remove the doubler fermions while maintaining exact chiral
symmetry on the lattice. Our lattice formulation enables us
to address non-perturbative questions in effective field
theories of baryons interacting with pions and in models
involving constituent quarks interacting with pions and
gluons. We show that a system containing a non-zero density
of static baryons interacting with pions can be studied on
the lattice without encountering complex action problems. In
our formulation one can also decide non-perturbatively if
the chiral quark model of Georgi and Manohar provides an
appropriate low-energy description of QCD. If so, one could
understand why the non-relativistic quark model works. ©
SISSA/ISAS 2004.},
Key = {fds245676}
}
@article{fds245736,
Author = {Bhattacharya, T and Chandrasekharan, S and Gupta, R and Lee, W and Sharpe, S},
Title = {NONPERTURBATIVE RENORMALIZATION CONSTANTS USING WARD
IDENTITIES.},
Journal = {Phys. Letts. B},
Volume = {461},
Number = {1-2},
Pages = {79-88},
Publisher = {Elsevier BV},
Year = {1999},
url = {http://dx.doi.org/10.1016/S0370-2693(99)00796-0},
Abstract = {We extend the application of axial Ward identities to
calculate $b_A, b_P$ and $b_T$, coefficients that give the
mass dependence of the renormalization constants of the
corresponding bilinear operators in the quenched theory. The
extension relies on using operators with non-degenerate
quark masses. It allows a complete determination of the O(a)
improvement coefficients for bilinears in the quenched
approximation using Ward Identities alone. Only the scale
dependent normalization constants $Z_P^0$ (or $Z_S^0$) and
$Z_T$ are undetermined. We present results of a pilot
numerical study using hadronic correlators.},
Doi = {10.1016/S0370-2693(99)00796-0},
Key = {fds245736}
}
@article{fds303645,
Author = {Chandrasekharan, S},
Title = {Novel Quantum Monte Carlo Algorithms for
Fermions},
Year = {2001},
Month = {October},
url = {http://arxiv.org/abs/hep-lat/0110018v1},
Abstract = {Recent research shows that the partition function for a
class of models involving fermions can be written as a
statistical mechanics of clusters with positive definite
weights. This new representation of the model allows one to
construct novel algorithms. We illustrate this through
models consisting of fermions with and without spin. A
Hubbard type model with both attractive and repulsive
interactions becomes tractable using the new approach.
Precision results in the two dimensional attractive model
confirm a superfluid phase transition in the
Kosterlitz-Thouless universality class.},
Key = {fds303645}
}
@article{Chandrasekharan:2001cj,
Author = {Chandrasekharan, Shailesh},
Title = {Novel quantum Monte Carlo algorithms for
fermions},
Year = {2001},
url = {http://arxiv.org/pdf/hep-lat/0110018},
Abstract = {http://arxiv.org/abs/hep-lat/0110018},
Key = {Chandrasekharan:2001cj}
}
@book{fds4128,
Author = {S. Chandrasekharan},
Title = {NOVEL QUANTUM MONTE CARLO ALGORITHMS FOR
FERMIONS},
Booktitle = {Quantum Monte Carlo: Recent Advances and Common Problems in
Condensed Matter Physics and Field Theory},
Publisher = {EDIZIONI ETS},
Editor = {M. Compostrini and M.P. Lomardo and F. Paderiva},
Year = {2001},
Abstract = {Recent research shows that the partition function for a
class of models involving fermions can be written as a
statistical mechanics of clusters with positive definite
weights. This new representation of the model allows one to
construct novel algorithms. We illustrate this through
models consisting of fermions with and without spin. A
Hubbard type model with both attractive and repulsive
interactions becomes tractable using the new approach.
Precision results in the two dimensional attractive model
confirm a superfluid phase transition in the
Kosterlitz-Thouless universality class.},
Key = {fds4128}
}
@article{fds245710,
Author = {Podolsky, D and Berkeley, UC and Chandrasekharan, S and Vishwanath,
A and Berkeley, LBL},
Title = {Novel transitions in S=1 spinor condensates and XY
Ashkin-Teller universality},
Journal = {arXiv:0707.0695 [cond-mat.stat-mech]},
Year = {2007},
Abstract = {We study spin-1 polar spinor condensates with magnetic
anisotropy, in two spatial dimensions at finite
temperatures. The topological binding of vorticity to
nematic disclinations leads to a rich phase diagram, which
is captured by a U(1) version of the Ashkin-Teller model. In
particular, a "cascaded" Kosterlitz-Thouless critical point,
with two diverging scales, is predicted. Numerical
simulations are performed to check our picture.},
Key = {fds245710}
}
@article{Yoo05_HFsign,
Author = {Yoo, J and Chandrasekharan, S and Kaul, RK and Ullmo, D and Baranger,
HU},
Title = {On the Sign Problem in the Hirsch-Fye Algorithm for Impurity
Problems},
Journal = {J. Phys. A: Math. and General},
Volume = {38},
Number = {48},
Pages = {10307},
Publisher = {cond-mat/0412771},
Year = {2005},
url = {http://www.phy.duke.edu/research/cmtheory/bg/paper/yooCKUB05_hfsign.pdf},
Abstract = {We show that there is no fermion sign problem in the Hirsch
and Fye algorithm for the single-impurity Anderson model.
Beyond the particle-hole symmetric case for which a simple
proof exists, this has been known only empirically. Here we
prove the nonexistence of a sign problem for the general
case by showing that each spin trace for a given Ising
configuration is separately positive. We further use this
insight to analyse under what conditions orbitally
degenerate Anderson models or the two-impurity Anderson
model develop a sign. © 2005 IOP Publishing
Ltd.},
Doi = {10.1088/0305-4470/38/48/004},
Key = {Yoo05_HFsign}
}
@article{fds323136,
Author = {Ayyar, V and Chandrasekharan, S},
Title = {Origin of fermion masses without spontaneous symmetry
breaking},
Journal = {Physical Review D},
Volume = {93},
Number = {8},
Publisher = {American Physical Society (APS)},
Year = {2016},
Month = {April},
url = {http://dx.doi.org/10.1103/PhysRevD.93.081701},
Abstract = {Using large scale Monte Carlo calculations in a simple three
dimensional lattice fermion model, we establish the
existence of a second order quantum phase transition between
a massless fermion phase and a massive one, both of which
have the same symmetries. This shows that fermion masses can
arise due to dynamics without the need for spontaneous
symmetry breaking. Universality suggests that this alternate
origin of the fermion mass should be of fundamental
interest.},
Doi = {10.1103/PhysRevD.93.081701},
Key = {fds323136}
}
@article{fds303643,
Author = {Chandrasekharan, S and Wiese, U-J},
Title = {Partition Functions of Strongly Correlated Electron Systems
as "Fermionants"},
Year = {2011},
Month = {August},
url = {http://arxiv.org/abs/1108.2461v1},
Abstract = {We introduce a new mathematical object, the "fermionant"
${\mathrm{Ferm}}_N(G)$, of type $N$ of an $n \times n$
matrix $G$. It represents certain $n$-point functions
involving $N$ species of free fermions. When N=1, the
fermionant reduces to the determinant. The partition
function of the repulsive Hubbard model, of geometrically
frustrated quantum antiferromagnets, and of Kondo lattice
models can be expressed as fermionants of type N=2, which
naturally incorporates infinite on-site repulsion. A
computation of the fermionant in polynomial time would solve
many interesting fermion sign problems.},
Key = {fds303643}
}
@article{fds212507,
Author = {S. Chandrasekharan and U.-J. Wiese},
Title = {Partition Functions of Strongly Correlated Electron Systems
as 'Fermionants'.},
Journal = {arXiv:1108.2461},
Year = {2011},
Month = {July},
url = {http://arxiv.org/abs/arXiv:1108.2461},
Abstract = {We introduce a new mathematical object, the "fermionant"
${\mathrm{Ferm}}_N(G)$, of type $N$ of an $n \times n$
matrix $G$. It represents certain $n$-point functions
involving $N$ species of free fermions. When N=1, the
fermionant reduces to the determinant. The partition
function of the repulsive Hubbard model, of geometrically
frustrated quantum antiferromagnets, and of Kondo lattice
models can be expressed as fermionants of type N=2, which
naturally incorporates infinite on-site repulsion. A
computation of the fermionant in polynomial time would solve
many interesting fermion sign problems.},
Key = {fds212507}
}
@article{Bietenholz:1996qc,
Author = {Bietenholz, W. and Brower, R. and Chandrasekharan, S. and Wiese, U. J.},
Title = {Perfect lattice actions for staggered fermions},
Journal = {Nucl. Phys. B},
Volume = {495},
Pages = {285-305},
Year = {1997},
url = {http://arxiv.org/pdf/hep-lat/9612007},
Abstract = {http://arxiv.org/abs/hep-lat/9612007},
Key = {Bietenholz:1996qc}
}
@article{fds245727,
Author = {Bietenholz, W and Brower, R and Chandrasekharan, S and Wiese,
UJ},
Title = {PERFECT LATTICE ACTIONS FOR STAGGERED FERMIONS},
Journal = {Nucl. Phys. B},
Volume = {495},
Number = {1-2},
Pages = {285-305},
Publisher = {Elsevier BV},
Year = {1997},
url = {http://dx.doi.org/10.1016/S0550-3213(97)00195-8},
Abstract = {We construct a perfect lattice action for staggered fermions
by blocking from the continuum. The locality, spectrum and
pressure of such perfect staggered fermions are discussed.
We also derive a consistent fixed point action for free
gauge fields and discuss its locality as well as the
resulting static quark-antiquark potential. This provides a
basis for the construction of (classically) perfect lattice
actions for QCD using staggered fermions.},
Doi = {10.1016/S0550-3213(97)00195-8},
Key = {fds245727}
}
@article{Bietenholz:1997kr,
Author = {Bietenholz, W. and Brower, R. and Chandrasekharan, S. and Wiese, U. J.},
Title = {Perfect lattice topology: The quantum rotor as a test
case},
Journal = {Phys. Lett. B},
Volume = {407},
Pages = {283-289},
Year = {1997},
url = {http://arxiv.org/pdf/hep-lat/9704015},
Abstract = {http://arxiv.org/abs/hep-lat/9704015},
Key = {Bietenholz:1997kr}
}
@article{fds245726,
Author = {Bietenholz, W and Brower, R and Chandrasekharan, S and Wiese,
UJ},
Title = {PERFECT LATTICE TOPOLOGY: THE QUANTUM ROTOR AS A TEST
CASE},
Journal = {Phys. Lett. B},
Volume = {407},
Number = {3-4},
Pages = {283-289},
Publisher = {Elsevier BV},
Year = {1997},
url = {http://dx.doi.org/10.1016/S0370-2693(97)00742-9},
Abstract = {Lattice actions and topological charges that are classically
and quantum mechanically perfect (i.e. free of lattice
artifacts) are constructed analytically for the quantum
rotor. It is demonstrated that the Manton action is
classically perfect while the Villain action is quantum
perfect. The geometric construction for the topological
charge is only perfect at the classical level. The quantum
perfect lattice topology associates a topological charge
distribution, not just a single charge, with each lattice
field configuration. For the quantum rotor with the
classically perfect action and topological charge, the
remaining cut-off effects are exponentially
suppressed.},
Doi = {10.1016/S0370-2693(97)00742-9},
Key = {fds245726}
}
@article{fds245713,
Author = {Chandrasekharan, S and Jiang, FJ},
Title = {Phase diagram of two-color lattice QCD in the chiral
limit},
Journal = {Phys. Rev. D},
Volume = {74},
Number = {1},
Pages = {014506},
Publisher = {American Physical Society (APS)},
Year = {2006},
ISSN = {1550-7998},
url = {http://link.aps.org/doi/10.1103/PhysRevD.74.014506},
Abstract = {We study thermodynamics of strongly coupled lattice QCD with
two colors of massless staggered fermions as a function of
the baryon chemical potential μ in 3+1 dimensions using a
new cluster algorithm. We find evidence that the model
undergoes a weak first order phase transition at μ=0 which
becomes second order at a finite μ. Symmetry considerations
suggest that the universality class of these phase
transitions should be governed by a O(N)×O(2) field theory
with collinear order, with N=3 at μ=0 and N=2 at μ≠0.
The universality class of the second order phase transition
at μ≠0 appears to be governed by the decoupled XY fixed
point present in the O(2)×O(2) field theory. Finally we
show that the quantum (T=0) phase transition as a function
of μ is a second order mean field transition.},
Doi = {10.1103/PhysRevD.74.014506},
Key = {fds245713}
}
@article{fds184647,
Author = {D. Podolski and S. Chandrasekharan and A.Vishwanath},
Title = {Phase Transitions of S=1 Spinor Condensates in an optical
lattice},
Journal = {Physical Review B},
Volume = {80},
Pages = {214513},
Year = {2009},
url = {http://prb.aps.org/abstract/PRB/v80/i21/e214513},
Abstract = {We study the phase diagram of spin-one polar condensates in
a two dimensional optical lattice with magnetic anisotropy.
We show that the topological binding of vorticity to nematic
disclinations allows for a rich variety of phase
transitions. These include Kosterlitz-Thouless-like
transitions with a superfluid stiff ness jump that can be
experimentally tuned to take a continuous set of values, and
a new cascaded Kosterlitz-Thouless" transition,
characterized by two divergent length scales. For higher
boson spin S, the thermal phase transitions are strongly
a ffected by the parity of S.},
Key = {fds184647}
}
@article{Podolsky:2007x,
Author = {Podolsky, D and Chandrasekharan, S and Vishwanath,
A},
Title = {Phase Transitions of S=1 Spinor Condensates in an Optical
Lattice},
Journal = {Phys. Rev. B. (accepted)},
Volume = {80},
Number = {21},
Publisher = {American Physical Society (APS)},
Year = {2007},
ISSN = {1098-0121},
url = {http://hdl.handle.net/10161/3298 Duke open
access},
Abstract = {http://arxiv.org/abs/arXiv:0707.0695 [cond-mat]},
Doi = {10.1103/PhysRevB.80.214513},
Key = {Podolsky:2007x}
}
@article{Chandrasekharan:2006tz,
Author = {Chandrasekharan, Shailesh and Jiang, Fu-Jiun},
Title = {Phase-diagram of two-color lattice QCD in the chiral
limit},
Journal = {Phys. Rev.},
Volume = {D74},
Pages = {014506},
Year = {2006},
url = {http://arxiv.org/pdf/hep-lat/0602031},
Abstract = {http://arxiv.org/abs/hep-lat/0602031},
Key = {Chandrasekharan:2006tz}
}
@article{fds375114,
Author = {Liu, H and Bhattacharya, T and Chandrasekharan, S and Gupta,
R},
Title = {Phases of 2d massless QCD with qubit regularization},
Journal = {Physical Review D: Particles, Fields, Gravitation and
Cosmology},
Publisher = {American Physical Society},
Year = {2023},
Month = {December},
url = {http://dx.doi.org/10.48550/arXiv.2312.17734},
Abstract = {We investigate the possibility of reproducing the continuum
physics of 2d SU(N) gauge theory coupled to a single flavor
of massless Dirac fermions using qubit regularization. The
continuum theory is described by N free fermions in the
ultraviolet (UV) and a coset Wess-Zumino-Witten (WZW) model
in the infrared (IR). In this work, we explore how well
these features can be reproduced using the Kogut-Susskind
Hamiltonian with a finite-dimensional link Hilbert space and
a generalized Hubbard coupling. Using strong coupling
expansions, we show that our model exhibits a gapped dimer
phase and another phase described by a spin-chain.
Furthermore, for N=2, using tensor network methods, we show
that there is a second-order phase transition between these
two phases. The critical theory at the transition can be
understood as an SU(2)_1 WZW model, using which we determine
the phase diagram of our model quantitatively. Using the
confinement properties of the model we argue how the UV
physics of free fermions could also emerge, but may require
further modifications to our model.},
Doi = {10.48550/arXiv.2312.17734},
Key = {fds375114}
}
@article{Brower:2001cz,
Author = {Brower, R. and Chandrasekharan, S. and Negele, J. W. and Wiese, U. J.},
Title = {Physical observables from lattice QCD at fixed
topology},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {106},
Pages = {581-583},
Year = {2002},
url = {http://arxiv.org/pdf/hep-lat/0110121},
Abstract = {http://arxiv.org/abs/hep-lat/0110121},
Key = {Brower:2001cz}
}
@article{fds245746,
Author = {Brower, R and Chandrasekharan, S and Negele, JW and Wiese,
UJ},
Title = {PHYSICAL OBSERVABLES FROM LATTICE QCD AT FIXED
TOPOLOGY},
Journal = {Nucl. Phys. B (Proc. Suppl.)},
Volume = {106},
Pages = {581},
Publisher = {Elsevier BV},
Year = {2002},
url = {http://dx.doi.org/10.1016/S0920-5632(01)01784-4},
Abstract = {Because present Monte Carlo algorithms for lattice QCD may
become trapped in a given topological charge sector when one
approaches the continuum limit, it is important to
understand the effect of calculating at fixed topology. In
this work, we show that although the restriction to a fixed
topological sector becomes irrelevant in the infinite volume
limit, it gives rise to characteristic finite size effects
due to contributions from all θ-vacua. We calculate these
effects and show how to extract physical results from
numerical data obtained at fixed topology.},
Doi = {10.1016/S0920-5632(01)01784-4},
Key = {fds245746}
}
@article{Bietenholz:1996pf,
Author = {Bietenholz, W. and Brower, R. and Chandrasekharan, S. and Wiese, U. J.},
Title = {Progress on perfect lattice actions for QCD},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {53},
Pages = {921-934},
Year = {1997},
url = {http://arxiv.org/pdf/hep-lat/9608068},
Abstract = {http://arxiv.org/abs/hep-lat/9608068},
Key = {Bietenholz:1996pf}
}
@article{fds245730,
Author = {Bietenholz, W and Brower, R and Chandrasekharan, S and Wiese,
UJ},
Title = {PROGRESS ON PERFECT LATTICE ACTIONS FOR QCD},
Journal = {Nucl. Phys. B (Proc. Suppl.)},
Volume = {53},
Number = {1-3},
Pages = {921-934},
Publisher = {Elsevier BV},
Year = {1997},
url = {http://dx.doi.org/10.1016/S0920-5632(96)00818-3},
Abstract = {We describe a number of aspects in our attempt to construct
an approximately perfect lattice action for QCD. Free quarks
are made optimally local on the whole renormalized
trajectory and their couplings are then truncated by
imposing 3-periodicity. The spectra of these short ranged
fermions are excellent approximations to continuum spectra.
The same is true for free gluons. We evaluate the
corresponding perfect quark-gluon vertex function,
identifying in particular the ``perfect clover term''. First
simulations for heavy quarks show that the mass is strongly
renormalized, but again the renormalized theory agrees very
well with continuum physics. Furthermore we describe the
multigrid formulation for the non-perturbative perfect
action and we present the concept of an exactly (quantum)
perfect topological charge on the lattice.},
Doi = {10.1016/S0920-5632(96)00818-3},
Key = {fds245730}
}
@article{fds245668,
Author = {Zou, H and Liu, Y and Lai, CY and Unmuth-Yockey, J and Yang, LP and Bazavov, A and Xie, ZY and Xiang, T and Chandrasekharan, S and Tsai, SW and Meurice, Y},
Title = {Progress towards quantum simulating the classical O(2)
model},
Journal = {Physical Review A - Atomic, Molecular, and Optical
Physics},
Volume = {90},
Number = {6},
Publisher = {American Physical Society (APS)},
Year = {2014},
Month = {December},
ISSN = {1050-2947},
url = {http://dx.doi.org/10.1103/PhysRevA.90.063603},
Abstract = {We connect explicitly the classical O(2) model in 1+1
dimensions, a model sharing important features with U(1)
lattice gauge theory, to physical models potentially
implementable on optical lattices and evolving at physical
time. Using the tensor renormalization-group formulation, we
take the time continuum limit and check that
finite-dimensional projections used in recent proposals for
quantum simulators provide controllable approximations of
the original model. We propose two-species Bose-Hubbard
models corresponding to these finite-dimensional projections
at strong coupling and discuss their possible
implementations on optical lattices using a Rb87 and K41
Bose-Bose mixture.},
Doi = {10.1103/PhysRevA.90.063603},
Key = {fds245668}
}
@article{Brower:1997ha,
Author = {Brower, R and Chandrasekharan, S and Wiese, UJ},
Title = {QCD as a quantum link model},
Journal = {Physical Review D},
Volume = {60},
Number = {9},
Pages = {DUMMY42},
Year = {1999},
ISSN = {0556-2821},
url = {http://arxiv.org/pdf/hep-th/9704106},
Abstract = {QCD is constructed as a lattice gauge theory in which the
elements of the link matrices are represented by
non-commuting operators acting in a Hubert space. The
resulting quantum link model for QCD is formulated with a
fifth Euclidean dimension, whose extent resembles the
inverse gauge coupling of the resulting fourdimensional
theory after dimensional reduction. The inclusion of quarks
is natural in Shamir's variant of Kaplan's fermion method,
which does not require fine-tuning to approach the chiral
limit. A rishon representation in terms of fermionic
constituents of the gluons is derived and the quantum link
Hamiltonian for QCD with a U(N) gauge symmetry is expressed
in terms of glueball, meson and constituent quark operators.
The new formulation of QCD is promising both from an
analytic and from a computational point of view. ©1999 The
American Physical Society.},
Doi = {10.1103/PhysRevD.60.094502},
Key = {Brower:1997ha}
}
@article{fds303654,
Author = {Brower, R and Chandrasekharan, S and Wiese, UJ},
Title = {QCD AS A QUANTUM LINK MODEL},
Journal = {Phys. Rev. D},
Volume = {60},
Number = {9},
Pages = {094502},
Publisher = {American Physical Society (APS)},
Year = {1999},
url = {http://arxiv.org/abs/hep-th/9704106v1},
Abstract = {QCD is constructed as a lattice gauge theory in which the
elements of the link matrices are represented by
non-commuting operators acting in a Hilbert space. The
resulting quantum link model for QCD is formulated with a
fifth Euclidean dimension, whose extent resembles the
inverse gauge coupling of the resulting four-dimensional
theory after dimensional reduction. The inclusion of quarks
is natural in Shamir's variant of Kaplan's fermion method,
which does not require fine-tuning to approach the chiral
limit. A rishon representation in terms of fermionic
constituents of the gluons is derived and the quantum link
Hamiltonian for QCD with a U(N) gauge symmetry is expressed
in terms of glueball, meson and constituent quark operators.
The new formulation of QCD is promising both from an
analytic and from a computational point of
view.},
Doi = {10.1103/PhysRevD.60.094502},
Key = {fds303654}
}
@article{Chandrasekharan:2000ew,
Author = {Chandrasekharan, Shailesh},
Title = {QCD at a finite density of static quarks},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {94},
Pages = {71-78},
Year = {2001},
url = {http://arxiv.org/pdf/hep-lat/0011022},
Abstract = {http://arxiv.org/abs/hep-lat/0011022},
Key = {Chandrasekharan:2000ew}
}
@article{fds245743,
Author = {Chandrasekharan, S},
Title = {QCD AT A FINITE DENSITY OF STATIC QUARKS.},
Journal = {Nucl. Phys. B (Proc. Suppl.)},
Volume = {94},
Number = {1-3},
Pages = {71-78},
Publisher = {Elsevier BV},
Year = {2001},
url = {http://dx.doi.org/10.1016/S0920-5632(01)00936-7},
Abstract = {Recently, cluster methods have been used to solve a variety
of sign problems including those that arise in the presence
of fermions. In all cases an analytic partial re-summation
over a class of configurations in the path integral was
necessary. Here the new ideas are illustrated using the
example of QCD at a finite density of static quarks. In this
limit the sign problem simplifies since the fermionic part
decouples. Furthermore, the problem can be solved completely
when the gauge dynamics is replaced by a Potts model. On the
other hand in QCD with light quarks the solution will
require a partial re-summation over both fermionic and gauge
degrees of freedom. The new approach points to unexplored
directions in the search for a solution to this more
challenging sign problem.},
Doi = {10.1016/S0920-5632(01)00936-7},
Key = {fds245743}
}
@article{Brower:2003yx,
Author = {Brower, R and Chandrasekharan, S and Negele, JW and Wiese,
UJ},
Title = {QCD at fixed topology},
Journal = {Phys. Lett. B},
Volume = {560},
Number = {1-2},
Pages = {64-74},
Publisher = {Elsevier BV},
Year = {2003},
url = {http://arxiv.org/pdf/hep-lat/0302005},
Abstract = {http://arxiv.org/abs/hep-lat/0302005},
Doi = {10.1016/S0370-2693(03)00369-1},
Key = {Brower:2003yx}
}
@article{fds303640,
Author = {Chandrasekharan, S and Li, A},
Title = {Quantum critical behavior in three dimensional lattice
Gross-Neveu models},
Journal = {Physical Review D - Particles, Fields, Gravitation and
Cosmology},
Volume = {88},
Number = {2},
Pages = {021701},
Publisher = {American Physical Society (APS)},
Year = {2013},
Month = {July},
url = {http://arxiv.org/abs/1304.7761v1},
Abstract = {We study quantum critical behavior in three dimensional
lattice Gross-Neveu models containing two four-component
massless Dirac fermions. We focus on two models with SU(2)
flavor symmetry and either a Z2 or a U(1) chiral symmetry.
Both models could not be studied earlier due to sign
problems. We use the fermion bag approach which is free of
sign problems and compute critical exponents at the phase
transitions. We estimate ν=0.83(1), η=0.62(1),
ηψ=0.38(1) in the Z2 and ν=0.849(8), η=0.633(8),
ηψ=0.373(3) in the U(1) model. © 2013 American Physical
Society.},
Doi = {10.1103/PhysRevD.88.021701},
Key = {fds303640}
}
@article{fds323137,
Author = {Chandrasekharan, S},
Title = {Quantum critical behavior with massless staggered fermions
in three dimensions},
Journal = {Proceedings of Science},
Volume = {29-July-2013},
Pages = {049},
Year = {2013},
Month = {January},
url = {http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=187},
Abstract = {We report on studies of quantum critical behavior in three
dimensional lattice Gross-Neveu models with one flavor of
staggered fermions. We focus on two models, one with
SU(2)×Z2 symmetry and the other with an SU(2)×U(1)
symmetry. Both these models could not be studied earlier
with conventional Monte Carlo methods due to sign problems.
However, the fermion bag approach is free of sign problems
for these models and allows us to compute the critical
exponents at the quantum phase transition that separates the
massless fermion phase at small couplings and the massive
fermion phase at large couplings. Our results help resolve
some old puzzles in the field.},
Key = {fds323137}
}
@article{fds365313,
Author = {Liu, H and Chandrasekharan, S and Kaul, R},
Title = {Quantum Critical Phenomena in an O(4) Fermion
Chain},
Journal = {PoS LATTICE2019 (2019) 222},
Year = {2020},
Month = {August},
url = {http://dx.doi.org/10.22323/1.363.0222},
Abstract = {We construct a fermionic lattice model containing
interacting spin-half fermions with an O(4) symmetry. In
addition the model contains a Z2 chiral symmetry which
prevents a fermion mass term. Our model is motivated by the
ability to study its physics using the meron-cluster
algorithm. By adding a strong repulsive Hubbard interaction
U, we can transform it into the regular Heisenberg
anti-ferromagnet. While we can study our model in any
dimension, as a first project we study it in one spatial
dimension. We discover that our model at U=0 can be
described as a lattice-regularized 2-flavor Gross-Neveu
model, where fermions become massive since the Z2 chiral
symmetry of the model is spontaneously broken. We show
numerically that the theory remains massive when U is small.
At large values of U the model is equivalent to the
isotropic spin-half anti-ferromagnetic chain, which is
massless for topological reasons. This implies that our
model has a quantum phase transition from a Z2 broken
massive phase to a topologically massless phase as we
increase U. We present results obtained from our quantum
Monte Carlo method near this phase transition.},
Doi = {10.22323/1.363.0222},
Key = {fds365313}
}
@article{fds360681,
Author = {Hanqing Liu and Emilie Huffman and Shailesh Chandrasekharan and Ribhu
K. Kaul},
Title = {Quantum Criticality of Anti-ferromagnetism and
Superconductivity with Relativity},
Year = {2021},
Month = {September},
Abstract = {We study a quantum phase transition from a massless to
massive Dirac fermion phase in a new two-dimensional
bipartite lattice model of electrons that is amenable to
sign-free quantum Monte Carlo simulations. Importantly,
interactions in our model are not only invariant under
\SU(2) symmetries of spin and charge like the Hubbard model,
but they also preserve an Ising like electron spin-charge
flip symmetry. From unbiased fermion bag Monte Carlo
simulations with up to 2304 sites, we show that the massive
fermion phase spontaneously breaks this Ising symmetry,
picking either anti-ferromagnetism or superconductivity and
that the transition at which both orders are simultaneously
quantum critical, belongs to a new "chiral spin-charge
symmetric" universality class. We explain our observations
using effective potential and renormalization group
calculations within the framework of a continuum field
theory.},
Key = {fds360681}
}
@article{fds368519,
Author = {Liu, H and Huffman, E and Chandrasekharan, S and Kaul,
RK},
Title = {Quantum Criticality of Antiferromagnetism and
Superconductivity with Relativity.},
Journal = {Physical review letters},
Volume = {128},
Number = {11},
Pages = {117202},
Year = {2022},
Month = {March},
url = {http://dx.doi.org/10.1103/physrevlett.128.117202},
Abstract = {We study a quantum phase transition from a massless to
massive Dirac fermion phase in a new two-dimensional
bipartite lattice model of electrons that is amenable to
sign-free quantum Monte Carlo simulations. Importantly,
interactions in our model are not only invariant under SU(2)
symmetries of spin and charge like the Hubbard model, but
they also preserve an Ising-like electron spin-charge flip
symmetry. From unbiased fermion bag Monte Carlo simulations
with up to 2304 sites, we show that the massive fermion
phase spontaneously breaks this Ising symmetry, picking
either antiferromagnetism or superconductivity, and that the
transition at which both orders are simultaneously quantum
critical belongs to a new "chiral spin-charge symmetric"
universality class. We explain our observations using
effective potential and renormalization group calculations
within the framework of a continuum field
theory.},
Doi = {10.1103/physrevlett.128.117202},
Key = {fds368519}
}
@article{Chandrasekharan:1996ih,
Author = {Chandrasekharan, S. and Wiese, U. J.},
Title = {Quantum link models: A discrete approach to gauge
theories},
Journal = {Nucl. Phys. B},
Volume = {492},
Pages = {455-474},
Year = {1997},
url = {http://arxiv.org/pdf/hep-lat/9609042},
Abstract = {http://arxiv.org/abs/hep-lat/9609042},
Key = {Chandrasekharan:1996ih}
}
@article{fds245729,
Author = {Chandrasekharan, S and Wiese, UJ},
Title = {QUANTUM LINK MODELS: A DISCRETE APPROACH TO GAUGE
THEORIES},
Journal = {Nucl. Phys. B},
Volume = {492},
Number = {1-2},
Pages = {455-474},
Publisher = {Elsevier BV},
Year = {1997},
url = {http://dx.doi.org/10.1016/S0550-3213(97)80041-7},
Abstract = {We construct lattice gauge theories in which the elements of
the link matrices are represented by non-commuting operators
acting in a Hilbert space. These quantum link models are
related to ordinary lattice gauge theories in the same way
as quantum spin models are related to ordinary classical
spin systems. Here U(1) and SU(2) quantum link models are
constructed explicitly. As Hamiltonian theories quantum link
models are nonrelativistic gauge theories with potential
applications in condensed matter physics. When formulated
with a fifth Euclidean dimension, universality arguments
suggest that dimensional reduction to four dimensions
occurs. Hence, quantum link models are also reformulations
of ordinary quantum field theories and are applicable to
particle physics, for example to QCD. The configuration
space of quantum link models is discrete and hence their
numerical treatment should be simpler than that of ordinary
lattice gauge theories with a continuous configuration
space.},
Doi = {10.1016/S0550-3213(97)80041-7},
Key = {fds245729}
}
@article{PhysRevB.72.024525,
Author = {Lee, JW and Chandrasekharan, S and Baranger, HU},
Title = {Quantum Monte Carlo Study of Disordered Fermions},
Journal = {Phys. Rev. B},
Volume = {72},
Number = {2},
Pages = {024525},
Publisher = {cond-mat/0411306},
Year = {2005},
ISSN = {1098-0121},
url = {http://dx.doi.org/10.1103/PhysRevB.72.024525},
Abstract = {We study a strongly correlated fermionic model with
attractive interactions in the presence of disorder in two
spatial dimensions. Our model has been designed so that it
can be solved using the recently discovered meron-cluster
approach. Although the model is unconventional it has the
same symmetries as the Hubbard model. Since the naive
algorithm is inefficient, we develop an algorithm by
combining the meron-cluster technique with the directed-loop
update. This combination allows us to compute the pair
susceptibility and the winding number susceptibility
accurately. We find that the s -wave superconductivity,
present in the clean model, does not disappear until the
disorder reaches a temperature dependent critical strength.
The critical behavior as a function of disorder close to the
phase transition belongs to the Berezinky-Kosterlitz-Thouless
universality class as expected. The fermionic degrees of
freedom, although present, do not appear to play an
important role near the phase transition. © 2005 The
American Physical Society.},
Doi = {10.1103/PhysRevB.72.024525},
Key = {PhysRevB.72.024525}
}
@article{fds245683,
Author = {Liu, D and Chandrasekharan, S and Baranger, HU},
Title = {Quantum Phase Transition and Dynamically Enhanced Symmetry
in Quadruple Quantum Dot System},
Journal = {Physical Review Letters},
Volume = {105},
Number = {25},
Pages = {256801},
Year = {2010},
url = {http://www.ncbi.nlm.nih.gov/pubmed/21231607},
Abstract = {We propose a system of four quantum dots designed to study
the competition between three types of interactions:
Heisenberg, Kondo, and Ising. We find a rich phase diagram
containing two sharp features: a quantum phase transition
(QPT) between charge-ordered and charge-liquid phases and a
dramatic resonance in the charge liquid visible in the
conductance. The QPT is of the Kosterlitz-Thouless type with
a discontinuous jump in the conductance at the transition.
We connect the resonance phenomenon with the degeneracy of
three levels in the isolated quadruple dot and argue that
this leads to a Kondo-like emergent symmetry from left-right
Z2 to U(1).},
Doi = {10.1103/physrevlett.105.256801},
Key = {fds245683}
}
@article{PhysRevLett.97.115703,
Author = {Priyadarshee, A and Chandrasekharan, S and Lee, JW and Baranger,
HU},
Title = {Quantum Phase Transitions of Hard-Core Bosons in Background
Potentials},
Journal = {Phys. Rev. Lett.},
Volume = {97},
Number = {11},
Pages = {115703},
Year = {2006},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17025902},
Abstract = {We study the zero temperature phase diagram of hard-core
bosons in two dimensions subjected to three types of
background potentials: staggered, uniform, and random. In
all three cases there is a quantum phase transition from a
superfluid (at small potential) to a normal phase (at large
potential), but with different universality classes. As
expected, the staggered case belongs to the XY universality,
while the uniform potential induces a mean field transition.
The disorder driven transition is clearly different from
both; in particular, we find z approximately 1.4, nu
approximately 1, and beta approximately 0.6.},
Doi = {10.1103/physrevlett.97.115703},
Key = {PhysRevLett.97.115703}
}
@article{fds362089,
Author = {Liu, H and Chandrasekharan, S},
Title = {Qubit Regularization and Qubit Embedding
Algebras},
Journal = {Symmetry},
Volume = {14},
Number = {2},
Year = {2022},
Month = {February},
url = {https://www.mdpi.com/journal/symmetry/special_issues/New_Applications_Symmetry_Lattice_Field_Theory},
Abstract = {Qubit regularization is a procedure to regularize the
infinite dimensional local Hilbert space of bosonic fields
to a finite dimensional one, which is a crucial step when
trying to simulate lattice quantum field theories on a
quantum computer. When the qubit-regularized lattice quantum
fields preserve important symmetries of the original theory,
qubit regularization naturally enforces certain algebraic
structures on these quantum fields. We introduce the concept
of qubit embedding algebras (QEAs) to characterize this
algebraic structure associated with a qubit regularization
scheme. We show a systematic procedure to derive QEAs for
the O(N) lattice spin models and the SU(N) lattice gauge
theories. While some of the QEAs we find were discovered
earlier in the context of the D-theory approach, our method
shows that QEAs are far richer. A more complete
understanding of the QEAs could be helpful in recovering the
fixed points of the desired quantum field
theories.},
Doi = {10.3390/sym14020305},
Key = {fds362089}
}
@article{fds353934,
Author = {T. Bhattacharya and A. Buser and S. Chandrasekharan and R. Gupta and H. Singh},
Title = {Qubit regularization of asymptotic freedom},
Journal = {Physical Review Letters},
Year = {2020},
Month = {December},
url = {https://arxiv.org/abs/2012.02153},
Abstract = {https://arxiv.org/abs/2012.02153},
Key = {fds353934}
}
@article{fds356407,
Author = {Bhattacharya, T and Buser, A and Chandrasekharan, S and Gupta, R and Singh, H},
Title = {Qubit regularization of asymptotic freedom},
Journal = {Physical Review Letters},
Volume = {26},
Number = {17},
Pages = {172001},
Publisher = {American Physical Society},
Year = {2020},
Month = {December},
url = {http://dx.doi.org/10.1103/PhysRevLett.126.172001},
Abstract = {We provide strong evidence that the asymptotically free
(1+1)-dimensional non-linear O(3) sigma model can be
regularized using a quantum lattice Hamiltonian, referred to
as the "Heisenberg-comb", that acts on a Hilbert space with
only two qubits per spatial lattice site. The
Heisenberg-comb consists of a spin-half anti-ferromagnetic
Heisenberg-chain coupled anti-ferromagnetically to a second
local spin-half particle at every lattice site. Using a
world-line Monte Carlo method we show that the model
reproduces the universal step-scaling function of the
traditional model up to correlation lengths of 200,000 in
lattice units and argue how the continuum limit could
emerge. We provide a quantum circuit description of
time-evolution of the model and argue that near-term quantum
computers may suffice to demonstrate asymptotic
freedom.},
Doi = {10.1103/PhysRevLett.126.172001},
Key = {fds356407}
}
@article{fds346701,
Author = {Singh, H and Chandrasekharan, S},
Title = {Qubit regularization of the O (3) sigma model},
Journal = {Physical Review D},
Volume = {100},
Number = {5},
Year = {2019},
Month = {September},
url = {http://dx.doi.org/10.1103/PhysRevD.100.054505},
Abstract = {We construct a qubit regularization of the O(3) nonlinear
sigma model in two and three spatial dimensions using a
quantum Hamiltonian with two qubits per lattice site. Using
a worldline formulation and worm algorithms, we show that in
two spatial dimensions our model has a quantum critical
point where the well-known scale-invariant physics of the
three-dimensional Wilson-Fisher fixed point is reproduced.
In three spatial dimensions, we recover mean-field critical
exponents at a similar quantum critical point. These results
show that our qubit Hamiltonian is in the same universality
class as the traditional classical lattice model close to
the critical points. Simple modifications to our model also
allow us to study the physics of traditional lattice models
with O(2) and Z2 symmetries close to the corresponding
critical points.},
Doi = {10.1103/PhysRevD.100.054505},
Key = {fds346701}
}
@article{fds323135,
Author = {Huffman, E and Banerjee, D and Chandrasekharan, S and Wiese,
UJ},
Title = {Real-time evolution of strongly coupled fermions driven by
dissipation},
Journal = {Annals of Physics},
Volume = {372},
Pages = {309-319},
Publisher = {Elsevier BV},
Year = {2016},
Month = {September},
url = {http://dx.doi.org/10.1016/j.aop.2016.05.019},
Abstract = {We consider the real-time evolution of a strongly coupled
system of lattice fermions whose dynamics is driven entirely
by dissipative Lindblad processes, with linear or quadratic
quantum jump operators. The fermion 2-point functions obey a
closed set of differential equations, which can be solved
with linear algebra methods. The staggered occupation order
parameter of the t- V model decreases exponentially during
the dissipative time evolution. The structure factor
associated with the various Fourier modes shows the slowing
down of low-momentum modes, which is due to particle number
conservation. The processes with nearest-neighbor-dependent
Lindblad operators have a decay rate that is proportional to
the coordination number of the spatial lattice.},
Doi = {10.1016/j.aop.2016.05.019},
Key = {fds323135}
}
@article{Cecile:2008kp,
Author = {Cecile, D. J. and Chandrasekharan, Shailesh},
Title = {Role of the $\sigma$-resonance in determining the
convergence of chiral perturbation theory},
Journal = {Phys. Rev.},
Volume = {D77},
Pages = {091501},
Year = {2008},
url = {http://arxiv.org/pdf/0801.3823},
Abstract = {http://arxiv.org/abs/0801.3823},
Key = {Cecile:2008kp}
}
@article{fds245705,
Author = {Cecile, DJ and Chandrasekharan, S},
Title = {Role of the sigma-resonance in determining the convergence
of chiral perturbation theory},
Journal = {Phys. Rev. D (Rapid Communications)},
Volume = {77},
Number = {9},
Pages = {091501},
Publisher = {American Physical Society (APS)},
Year = {2008},
ISSN = {1550-7998},
url = {http://link.aps.org/doi/10.1103/PhysRevD.77.091501},
Abstract = {The dimensionless parameter $\xi = M_\pi^2/(16 \pi^2
F_\pi^2)$, where $F_\pi$ is the pion decay constant and
$M_\pi$ is the pion mass, is expected to control the
convergence of chiral perturbation theory applicable to QCD.
Here we demonstrate that a strongly coupled lattice gauge
theory model with the same symmetries as two-flavor QCD but
with a much lighter $\sigma$-resonance is different. Our
model allows us to study efficiently the convergence of
chiral perturbation theory as a function of $\xi$. We first
confirm that the leading low energy constants appearing in
the chiral Lagrangian are the same when calculated from the
$p$-regime and the $\epsilon$-regime as expected. However,
$\xi \lesssim 0.002$ is necessary before 1-loop chiral
perturbation theory predicts the data within 1%. For $\xi >
0.0035$ the data begin to deviate dramatically from 1-loop
chiral perturbation theory predictions. We argue that this
qualitative change is due to the presence of a light
$\sigma$-resonance in our model. Our findings may be useful
for lattice QCD studies.},
Doi = {10.1103/PhysRevD.77.091501},
Key = {fds245705}
}
@article{chandrasekharan:077901,
Author = {S. Chandrasekharan and F.-J. Jiang and M. Pepe and U.-J.
Wiese},
Title = {Rotor spectra, berry phases, and monopole fields: From
antiferromagnets to QCD},
Journal = {Physical Review D (Particles and Fields)},
Volume = {78},
Number = {7},
Pages = {077901},
Publisher = {APS},
Year = {2008},
url = {http://link.aps.org/abstract/PRD/v78/e077901},
Key = {chandrasekharan:077901}
}
@article{Cecile:2008gs,
Author = {Cecile, DJ and Chandrasekharan, S},
Title = {Sigma-resonance and convergence of chiral perturbation
theory},
Journal = {PoS},
Volume = {LATTICE2008},
Pages = {071},
Year = {2008},
url = {http://arxiv.org/abs/0810.2423v1},
Abstract = {http://arxiv.org/abs/0810.2423},
Key = {Cecile:2008gs}
}
@article{fds303644,
Author = {Chandrasekharan, S and Wiese, U-J},
Title = {SO(10) Unification of Color Superconductivity and Chiral
Symmetry Breaking?},
Year = {2000},
Month = {March},
url = {http://arxiv.org/abs/hep-ph/0003214v1},
Abstract = {Motivated by the SO(5) theory of high-temperature
superconductivity and antiferromagnetism, we ask if an
SO(10) theory unifies color superconductivity and chiral
symmetry breaking in QCD. The transition to the color
superconducting phase would then be analogous to a spin flop
transition. While the spin flop transition generically has a
unified SO(3) description, the SO(5) and SO(10) symmetric
fixed points are unstable, at least in (4 - epsilon)
dimensions, and require the fine-tuning of one additional
relevant parameter. If QCD is near the SO(10) fixed point,
it has interesting consequences for heavy ion collisions and
neutron stars.},
Key = {fds303644}
}
@article{Chandrasekharan:2000gk,
Author = {Chandrasekharan, Shailesh and Wiese, Uwe-Jens},
Title = {SO(10) unification of color superconductivity and chiral
symmetry breaking?},
Year = {2000},
url = {http://arxiv.org/pdf/hep-ph/0003214},
Abstract = {http://arxiv.org/abs/hep-ph/0003214},
Key = {Chandrasekharan:2000gk}
}
@article{fds4134,
Author = {S. Chandrasekharan and U.-J. Wiese},
Title = {SO(10) UNIFICATION OF COLOR SUPERCONDUCTIVITY AND CHIRAL
SYMMETRY BREAKING?},
Year = {2000},
Abstract = {Motivated by the SO(5) theory of high-temperature
superconductivity and antiferromagnetism, we ask if an
SO(10) theory unifies color superconductivity and chiral
symmetry breaking in QCD. The transition to the color
superconducting phase would then be analogous to a spin flop
transition. While the spin flop transition generically has a
unified SO(3) description, the SO(5) and SO(10) symmetric
fixed points are unstable, at least in (4 - epsilon)
dimensions, and require the fine-tuning of one additional
relevant parameter. If QCD is near the SO(10) fixed point,
it has interesting consequences for heavy ion collisions and
neutron stars.},
Key = {fds4134}
}
@article{Alford:2001ug,
Author = {Alford, Mark G. and Chandrasekharan, S. and Cox, J. and Wiese, U. J.},
Title = {Solution of the complex action problem in the Potts model
for dense QCD},
Journal = {Nucl. Phys. B},
Volume = {602},
Pages = {61-86},
Year = {2001},
url = {http://arxiv.org/pdf/hep-lat/0101012},
Abstract = {http://arxiv.org/abs/hep-lat/0101012},
Key = {Alford:2001ug}
}
@article{fds245744,
Author = {Alford, M and Chandrasekharan, S and Cox, J and Wiese,
UJ},
Title = {SOLUTION OF THE COMPLEX ACTION PROBLEM IN THE POTTS MODEL
FOR DENSE QCD.},
Journal = {Nucl. Phys. B},
Volume = {602},
Number = {1-2},
Pages = {61},
Publisher = {Elsevier BV},
Year = {2001},
url = {http://dx.doi.org/10.1016/S0550-3213(01)00068-2},
Abstract = {Monte Carlo simulations of lattice QCD at non-zero baryon
chemical potential $\mu$ suffer from the notorious complex
action problem. We consider QCD with static quarks coupled
to a large chemical potential. This leaves us with an SU(3)
Yang-Mills theory with a complex action containing the
Polyakov loop. Close to the deconfinement phase transition
the qualitative features of this theory, in particular its
Z(3) symmetry properties, are captured by the 3-d 3-state
Potts model. We solve the complex action problem in the
Potts model by using a cluster algorithm. The improved
estimator for the $\mu$-dependent part of the Boltzmann
factor is real and positive and is used for importance
sampling. We localize the critical endpoint of the first
order deconfinement phase transition line and find
consistency with universal 3-d Ising behavior. We also
calculate the static quark-quark, quark-anti-quark, and
anti-quark-anti-quark potentials which show screening as
expected for a system with non-zero baryon
density.},
Doi = {10.1016/S0550-3213(01)00068-2},
Key = {fds245744}
}
@article{fds303638,
Author = {Huffman, E and Chandrasekharan, S},
Title = {Solution to new sign problems with Hamiltonian Lattice
Fermions},
Journal = {PoS (LATTICE 2014) 058},
Year = {2014},
Month = {November},
url = {http://arxiv.org/abs/1411.7147v2},
Abstract = {We present a solution to the sign problem in a class of
particle-hole symmetric Hamiltonian lattice fermion models
on bipartite lattices using the idea of fermion bags. The
solution remains valid when the particle-hole symmetry is
broken through a staggered chemical potential term. This
solution allows, for the first time, simulations of some
massless four-fermion models with minimal fermion doubling
and with an odd number of fermion flavors using ultra-local
actions. One can thus study a variety of quantum phase
transitions that have remained unexplored so far due to sign
problems.},
Key = {fds303638}
}
@article{fds303639,
Author = {Huffman, EF and Chandrasekharan, S},
Title = {Solution to sign problems in half-filled spin-polarized
electronic systems},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {89},
Number = {11},
Pages = {111101},
Publisher = {American Physical Society (APS)},
Year = {2014},
Month = {March},
url = {http://arxiv.org/abs/1311.0034v1},
Abstract = {We solve the sign problem in a particle-hole symmetric
spin-polarized fermion model on bipartite lattices using the
idea of fermion bags. The solution can be extended to a
class of models at half filling but without particle-hole
symmetry. Attractive Hubbard models with an odd number of
fermion species can also be solved. Our solutions should
allow us to study quantum phase transitions that have
remained unexplored so far due to sign problems. © 2014
American Physical Society.},
Doi = {10.1103/PhysRevB.89.111101},
Key = {fds303639}
}
@article{fds225570,
Author = {E.F. Huffman and S. Chandrasekharan},
Title = {Solution to sign problems in half-filled spin-polarized
electronic systems},
Journal = {Phys. Rev. (Rapid Communications)},
Volume = {B89},
Pages = {111101},
Year = {2014},
Month = {February},
url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.111101},
Abstract = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.111101},
Doi = {10.1103/PhysRevB.89.111101},
Key = {fds225570}
}
@article{fds323133,
Author = {Huffman, E and Chandrasekharan, S},
Title = {Solution to sign problems in models of interacting fermions
and quantum spins.},
Journal = {Physical review. E},
Volume = {94},
Number = {4-1},
Pages = {043311},
Year = {2016},
Month = {October},
url = {http://dx.doi.org/10.1103/physreve.94.043311},
Abstract = {We show that solutions to fermion sign problems that are
found in the formulation where the path integral is expanded
in powers of the interaction in continuous time can be
extended to systems involving fermions interacting with
dynamical quantum spins. While these sign problems seem
unsolvable in the auxiliary field approach, solutions emerge
in the world-line representation of quantum spins. Combining
this idea with meron-cluster methods, we are able to further
extend the class of models that are solvable. We demonstrate
these solutions to sign problems by considering several
examples of strongly correlated systems that contain the
physics of semimetals, insulators, superfluidity, and
antiferromagnetism.},
Doi = {10.1103/physreve.94.043311},
Key = {fds323133}
}
@article{fds323235,
Author = {Hann, CT and Huffman, E and Chandrasekharan, S},
Title = {Solution to the sign problem in a frustrated quantum
impurity model},
Journal = {Annals of Physics},
Volume = {376},
Pages = {63-75},
Publisher = {Elsevier BV},
Year = {2017},
Month = {January},
url = {http://dx.doi.org/10.1016/j.aop.2016.11.006},
Abstract = {In this work we solve the sign problem of a frustrated
quantum impurity model consisting of three quantum spin-half
chains interacting through an anti-ferromagnetic Heisenberg
interaction at one end. We first map the model into a
repulsive Hubbard model of spin-half fermions hopping on
three independent one dimensional chains that interact
through a triangular hopping at one end. We then convert the
fermion model into an inhomogeneous one dimensional model
and express the partition function as a weighted sum over
fermion worldline configurations. By imposing a pairing of
fermion worldlines in half the space we show that all
negative weight configurations can be eliminated. This
pairing naturally leads to the original frustrated quantum
spin model at half filling and thus solves its sign
problem.},
Doi = {10.1016/j.aop.2016.11.006},
Key = {fds323235}
}
@article{PhysRevD.86.021701,
Author = {Chandrasekharan Shailesh},
Title = {Solutions to sign problems in lattice Yukawa
models},
Journal = {Phys. Rev. D},
Volume = {86},
Number = {2},
Pages = {021701},
Publisher = {American Physical Society},
Year = {2012},
Month = {July},
ISSN = {1550-7998},
url = {http://link.aps.org/doi/10.1103/PhysRevD.86.021701},
Abstract = {We prove that sign problems in the traditional approach to
some lattice Yukawa models can be completely solved when
fermions are formulated using fermion bags and bosons are
formulated in the worldline representation. We prove this
within the context of two examples of three-dimensional
models, symmetric under U L(1)×U R(1)×Z 2(parity)
transformations, one involving staggered fermions and the
other involving Wilson fermions. We argue that these models
have interesting quantum phase transitions that can now be
studied using Monte Carlo methods. © 2012 American Physical
Society.},
Doi = {10.1103/PhysRevD.86.021701},
Key = {PhysRevD.86.021701}
}
@book{fds4130,
Author = {S. Chandrasekharan},
Title = {SOLVING SIGN PROBLEMS WITH MERON ALGORITHMS},
Series = {Springer Proc. Phys. 86, pp 28-42},
Booktitle = {Computer Simulations in Condensed Matter Physics
XIII},
Publisher = {Springer},
Editor = {D.P. Landau and S.P.Lewis and H.-B.Shuttler},
Year = {2000},
Month = {January},
Key = {fds4130}
}
@article{Chandrasekharan:2000fr,
Author = {Chandrasekharan, S and Osborn, J},
Title = {Solving Sign Problems with Meron Algorithms},
Journal = {Springer Proc. Phys.},
Volume = {86},
Pages = {28-42},
Publisher = {SPRINGER-VERLAG BERLIN},
Editor = {Landau, DP and Lewis, SP and Schuttler, HB},
Year = {2000},
ISSN = {0930-8989},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000165950700004&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Key = {Chandrasekharan:2000fr}
}
@article{fds362721,
Author = {Zhou, J and Singh, H and Bhattacharya, T and Chandrasekharan, S and Gupta, R},
Title = {Spacetime symmetric qubit regularization of the
asymptotically free two-dimensional O(4)
model},
Journal = {Physical Review D: Particles, Fields, Gravitation and
Cosmology},
Volume = {105},
Number = {5},
Publisher = {American Physical Society},
Year = {2022},
Month = {March},
url = {http://dx.doi.org/10.1103/PhysRevD.105.054510},
Abstract = {We explore if space-time symmetric lattice field theory
models with a finite Hilbert space per lattice site can
reproduce asymptotic freedom in the two-dimensional O(4)O(4)
model. We focus on a simple class of such models with a five
dimensional local Hilbert space. We demonstrate how even the
simplest model reproduces asymptotic freedom within the
D-theory formalism but at the cost of increasing the size of
the Hilbert space through coupling several layers of a
two-dimensional lattice. We then argue that qubit
regularization can be viewed as an effective field theory
(EFT) even if the continuum limit cannot be reached, as long
as we can tune the model close enough to the continuum limit
where perturbation theory, or other analytical techniques,
become viable. We construct a simple lattice model on a
single layer with a four dimensional local Hilbert space
that acts like an excellent EFT of the original
theory.},
Doi = {10.1103/PhysRevD.105.054510},
Key = {fds362721}
}
@article{PhysRevLett.96.176802,
Author = {Kaul, Ribhu K. and Zar\'and, Gergely and Chandrasekharan,
Shailesh and Ullmo, Denis and Baranger, Harold
U.},
Title = {Spectroscopy of the Kondo Problem in a Box},
Journal = {Phys. Rev. Lett.},
Volume = {96},
Number = {17},
Pages = {176802},
Year = {2006},
Key = {PhysRevLett.96.176802}
}
@article{fds245711,
Author = {Kaul, RK and Zaránd, G and Chandrasekharan, S and Ullmo, D and Baranger, HU},
Title = {Spectroscopy of the Kondo Problem in a Box},
Journal = {Phys.Rev.Lett.},
Volume = {96},
Number = {17},
Pages = {176802},
Year = {2006},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/16712322},
Abstract = {Motivated by experiments on double quantum dots, we study
the problem of a single magnetic impurity confined in a
finite metallic host. We prove an exact theorem for the
ground state spin, and use analytic and numerical arguments
to map out the spin structure of the excitation spectrum of
the many-body Kondo-correlated state, throughout the weak to
strong coupling crossover. These excitations can be probed
in a simple tunneling-spectroscopy transport experiment; for
that situation we solve rate equations for the
conductance.},
Doi = {10.1103/physrevlett.96.176802},
Key = {fds245711}
}
@article{fds360682,
Author = {D. Banerjee and S. Chandrasekharan},
Title = {Sub-leading conformal dimensions at the O(4) Wilson-Fisher
fixed point},
Year = {2021},
Abstract = {In this work we focus on computing the conformal dimensions
D(j_L,j_R)D(j_L,j_R) of local fields that transform in an
irreducible representation of SU(2) \times SU(2)SU(2)×SU(2)
labeled with (j_L,j_R)(j_L,j_ R) at the O(4) Wilson-Fisher
fixed point using the Monte Carlo method. In the large
charge expansion, among the sectors with a fixed large value
of j = {\rm max}(j_L,j_R)j=max(j_L,j_R), the leading sector
has |j_L-j_R|=0 and the sub-leading one has |j_L-j_R| =1.
Since Monte Carlo calculations at large jj become
challenging in the traditional lattice formulation of the
O(4)model, a qubit regularized O(4)lattice model was used
recently to compute D(j,j). Here we extend those
calculations to the sub-leading sector. Our Monte Carlo
results up to j=20j=20 fit well to the form D(j,j-1)-D(j)
\sim \lambda_{1/2}/\sqrt{j} + \lambda_1/j +
\lambda_{3/2}/j^{3/2}, consistent with recent predictions of
the large charge expansion. Taking into account systematic
effects in our fitting procedures we estimate the two
leading coefficients to be \lambda_{1/2}=2.08(5),
\lambda_1=2.2(3).},
Key = {fds360682}
}
@article{fds368520,
Author = {Banerjee, D and Chandrasekharan, S},
Title = {Subleading conformal dimensions at the O(4) Wilson-Fisher
fixed point},
Journal = {Physical Review D},
Volume = {105},
Number = {3},
Pages = {L031507},
Year = {2022},
Month = {February},
url = {http://dx.doi.org/10.1103/PhysRevD.105.L031507},
Abstract = {In this work we focus on computing the conformal dimensions
D(jL,jR) of local fields that transform in an irreducible
representation of SU(2)×SU(2) labeled with (jL,jR) at the
O(4) Wilson-Fisher fixed point using the Monte Carlo method.
In the large charge expansion, among the sectors with a
fixed large value of j=max(jL,jR), the leading sector has
|jL-jR|=0 and the subleading one has |jL-jR|=1. Since Monte
Carlo calculations at large j become challenging in the
traditional lattice formulation of the O(4) model, a qubit
regularized O(4) lattice model was used recently to compute
D(j,j). Here we extend those calculations to the subleading
sector. Our Monte Carlo results in the range 2≤j≤20 fit
well to the expected large j expansion D(j,j-1)-D(j,j)∼λ0+λ1/2/j+λ1/j+λ3/2/j3/2,
but we have to assume that at least one of the purely
quantum mechanical contributions λ0 or λ1 is nonzero.
Assuming λ0=0 as conjectured recently, we find
λ1/2≈2.1(1), λ1≈2.3(2), and λ3/2≈1.2(2).},
Doi = {10.1103/PhysRevD.105.L031507},
Key = {fds368520}
}
@article{Chandrasekharan:2001dd,
Author = {Chandrasekharan Shailesh},
Title = {Superconductivity and chiral symmetry breaking with fermion
clusters},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {106},
Pages = {1025-1027},
Publisher = {Elsevier BV},
Year = {2002},
url = {http://arxiv.org/pdf/hep-lat/0110125},
Abstract = {http://arxiv.org/abs/hep-lat/0110125},
Doi = {10.1016/S0920-5632(01)01917-X},
Key = {Chandrasekharan:2001dd}
}
@article{fds303646,
Author = {Chandrasekharan, S and Li, A},
Title = {The generalized fermion bag approach},
Journal = {Proceedings of Science},
Volume = {Lattice 2011},
Pages = {058},
Year = {2011},
Month = {December},
url = {http://arxiv.org/abs/1111.5276v1},
Abstract = {We present a new approach to some four-fermion lattice field
theories which we call the generalized fermion bag approach.
The basic idea is to identify unpaired fermionic degrees of
freedom that cause sign problems and collect them in a bag.
Paired fermions usually act like bosons and do not lead to
sign problems. A resummation of all unpaired fermion degrees
of freedom inside the bag is sufficient to solve the fermion
sign problem in a variety of interesting cases. Using a
concept of duality we then argue that the size of the
fermion bags is small both at strong and weak couplings.
This allows us to construct efficient algorithms in both
these limits. Using the fermion bag approach, we study the
quantum phase transition of the 3D massless lattice
Thirrring model which is of interest in the context of
Graphene. Using our method we are able to solve the model on
lattices as large as 403 with moderate computational
resources. We obtain the precise location of the quantum
critical point and the values of the critical exponents
through this study.},
Key = {fds303646}
}
@article{fds245725,
Author = {Orginos, K and Bietenholz, W and Brower, R and Chandrasekharan, S and Wiese, UJ},
Title = {THE PERFECT QUARK GLUON VERTEX FUNCTION},
Journal = {Nucl. Phys. B (Proc. Suppl.)},
Volume = {63},
Number = {1-3},
Pages = {904-906},
Publisher = {Elsevier BV},
Year = {1998},
url = {http://dx.doi.org/10.1016/S0920-5632(97)00936-5},
Abstract = {We evaluate a perfect quark-gluon vertex function for QCD in
coordinate space and truncate it to a short range. We
present preliminary results for the charmonium spectrum
using this quasi-perfect action.},
Doi = {10.1016/S0920-5632(97)00936-5},
Key = {fds245725}
}
@article{Orginos:1997fh,
Author = {Orginos, K. and Bietenholz, W. and Brower, R. and Chandrasekharan, S. and Wiese, U. -J.},
Title = {The perfect quark-gluon vertex function},
Journal = {Nucl. Phys. Proc. Suppl.},
Volume = {63},
Pages = {904-906},
Year = {1998},
url = {http://arxiv.org/pdf/hep-lat/9709100},
Abstract = {http://arxiv.org/abs/hep-lat/9709100},
Key = {Orginos:1997fh}
}
@article{fds368518,
Author = {Maiti, S and Banerjee, D and Chandrasekharan, S and Marinkovic,
MK},
Title = {Three-dimensional Gross-Neveu model with two flavors of
staggered fermions},
Journal = {Proceedings of Science},
Volume = {396},
Year = {2022},
Month = {July},
Abstract = {We introduce a strongly interacting lattice field theory
model containing two flavors of massless staggered fermions
with two kind of interactions: (1) a lattice current-current
interaction, and (2) an on-site four-fermion interaction. At
weak couplings, we expect a massless fermion phase since our
interactions become irrelevant at long distances. At strong
couplings, based on previous studies, we argue that our
lattice model contains two different massive fermion phases
with different mechanisms of fermion mass generation. In one
phase, fermions become massive through Spontaneous Symmetry
Breaking (SSB) via the formation of a fermion bilinear
condensate. In the other phase, fermion mass arises through
a more exotic mechanism without the formation of any fermion
bilinear condensate. Our lattice model is free of sign
problems and can be studied using the fermion bag algorithm.
The longer term goal here is to study both these mass
generation phenomena in a single model and understand how
different phases come together.},
Key = {fds368518}
}
@article{fds375115,
Author = {Bhattacharya, T and Chandrasekharan, S and Gupta, R and Richardson,
TR and Singh, H},
Title = {Topological terms with qubit regularization and relativistic
quantum circuits},
Year = {2023},
Month = {October},
url = {http://dx.doi.org/10.48550/arXiv.2310.06805},
Abstract = {Qubit regularization provides a rich framework to explore
quantum field theories. The freedom to choose how the
important symmetries of the theory are embedded in the qubit
regularization scheme allows us to construct new lattice
models with rich phase diagrams. Some of the phases can
contain topological terms which lead to critical phases. In
this work we introduce and study the SU(3)-F qubit
regularization scheme to embed the SO(3) spin-symmetry. We
argue that qubit models in this regularization scheme
contain several phases including a critical phase which
describes the k = 1 Wess-Zumino-Witten (WZW) conformal field
theory (CFT) at long distances, and two massive phases one
of which is trvially gapped and the other which breaks the
lattice translation symmetry. We construct a simple
space-time Euclidean lattice model with a single coupling U
and study it using the Monte Carlo method. We show the model
has a critical phase at small U and a trivially massive
phase at large U with a first order transition separating
the two. Another feature of our model is that it is
symmetric under space-time rotations, which means the
temporal and spatial lattice spacing are connected to each
other. The unitary time evolution operator obtained by a
Wick rotation of the transfer matrix of our model can help
us compute the physics of the k = 1 WZW CFT in real time
without the need for tuning the temporal lattice spacing to
zero. We use this idea to introduce the concept of a
relativistic quantum circuit on a discrete space-time
lattice.},
Doi = {10.48550/arXiv.2310.06805},
Key = {fds375115}
}
@article{fds225572,
Author = {Haiyuan Zou and Yuzhi Liu and Chen-Yen Lai and J. Unmuth-Yockey and A.
Bazavov, Z.Y. Xie and T. Xiang and S. Chandrasekharan and S. -W.
Tsai, Y. Meurice},
Title = {Towards quantum computing for the classical O(2)
model},
Journal = {Phys. Rev. A},
Year = {2014},
url = {http://arxiv.org/abs/arXiv:1403.5238},
Abstract = {http://arxiv.org/abs/arXiv:1403.5238},
Key = {fds225572}
}
@article{fds245748,
Author = {Chandrasekharan, S},
Title = {UNEXPECTED RESULTS IN THE CHIRAL LIMIT WITH STAGGERED
FERMIONS},
Journal = {Physics Letters B},
Volume = {536},
Number = {1-2},
Pages = {72},
Publisher = {Elsevier BV},
Year = {2002},
Month = {January},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/S0370-2693(02)01816-6},
Abstract = {A cluster algorithm is constructed and applied to study the
chiral limit of the strongly coupled lattice Schwinger model
involving staggered fermions. The algorithm is based on a
novel loop representation of the model. Finite size scaling
of the chiral susceptibility based on data from lattices of
size up to $64\times 64$ indicates the absence of long range
correlations at strong couplings. Assuming that there is no
phase transition at a weaker coupling, the results imply
that all mesons acquire a mass at non-zero lattice spacings.
Although this does not violate any known physics, it is
surprising since typically one expects a single pion to
remain massless at non-zero lattice spacings in the
staggered fermion formulation.},
Doi = {10.1016/S0370-2693(02)01816-6},
Key = {fds245748}
}
@article{Chandrasekharan:2002ex,
Author = {Chandrasekharan, Shailesh},
Title = {Unexpected results in the chiral limit with staggered
fermions},
Journal = {Phys. Lett. B},
Volume = {536},
Pages = {72-78},
Year = {2002},
url = {http://arxiv.org/pdf/hep-lat/0203020},
Abstract = {http://arxiv.org/abs/hep-lat/0203020},
Key = {Chandrasekharan:2002ex}
}
@article{fds375117,
Author = {Singh, H and Bhattacharya, T and Chandrasekharan, S and Gupta,
R},
Title = {Vacuum Entanglement Harvesting in the Ising
Model},
Year = {2023},
Month = {February},
url = {http://dx.doi.org/10.48550/arXiv.2302.12858},
Abstract = {The low-energy states of quantum many body systems, such as
spin chains, are entangled. Using tensor network
computations, we demonstrate a protocol that distills Bell
pairs out of the ground state of the prototypical
transverse-field Ising model. We explore the behavior of
rate of entanglement distillation in various phases, and
possible optimizations of the protocol. Finally, we comment
on the protocol as we approach quantum criticality defining
a continuum field theory.},
Doi = {10.48550/arXiv.2302.12858},
Key = {fds375117}
}
@article{fds345676,
Author = {Singh, H and Chandrasekharan, S},
Title = {Worldline approach to few-body physics on the
Lattice},
Journal = {Proceedings of Science},
Volume = {334},
Year = {2018},
Month = {January},
Abstract = {We study the physics of two species of non-relativistic
hard-core bosons with attractive or repulsive delta function
interactions on a spacetime lattice using the worldline
formulation. By tuning the chemical potential carefully we
show that worm algorithms can efficiently sample the
worldline configurations in any fixed particle-number
sector. Since fermions can be treated as hard-core bosons up
to a permutation sign, we also apply this approach to
non-relativistic fermions. The fermion permutation sign is
treated as an observable in this approach and can be used to
extract energies for each particle-number sector. Since in
one dimension non-relativistic fermions can only permute due
to boundary effects, unlike the auxiliary field method, in
many cases our approach does not suffer from sign problems.
Using our method we discover limitations of the recently
proposed complex Langevin calculations in one
dimension.},
Key = {fds345676}
}
@article{fds245731,
Author = {Chandrasekharan, S and Huang, S-Z},
Title = {Z(3) TWISTED CHIRAL CONDENSATES IN QCD AT FINITE
TEMPERATURES},
Journal = {Phys. Rev. D},
Volume = {53},
Number = {9},
Pages = {5100-5104},
Year = {1996},
ISSN = {0556-2821},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10020507},
Abstract = {It was recently observed in a lattice QCD measurement that
the chiral condensate in the quenched approximation shows
dramatically different behavior in the three
$Z_3$-equivalent de-confined phases. We argue that this
phenomenon can be understood qualitatively as an effect of
$Z_3$ twists on fermionic fields. Quarks under these
$Z_3$-twists become global anyons and hence display
different thermodynamic properties. We further show that the
lattice data can be roughly modeled by a Nambu-Jona-Lasinio
type Lagrangian with a minimal coupling to a constant gauge
field $A_0=2\pi nT/3$ (with $n=0$, $\pm1$), which arises
naturally from the non-trivial phase of the Polyakov
line.},
Doi = {10.1103/physrevd.53.5100},
Key = {fds245731}
}
@article{Chandrasekharan:1995nf,
Author = {Chandrasekharan, S and Huang, S},
Title = {Z3 twisted chiral condensates in QCD at finite
temperatures},
Journal = {Physical Review D - Particles, Fields, Gravitation and
Cosmology},
Volume = {53},
Number = {9},
Pages = {5100-5104},
Year = {1996},
url = {http://arxiv.org/pdf/hep-ph/9512323},
Abstract = {It was recently observed in a lattice QCD measurement that
the chiral condensate in the quenched approximation shows
dramatically different behavior in the three Z3-equivalent
deconfined phases. We argue that this phenomenon can be
understood qualitatively as an effect of Z3 twists on
fermionic fields. Quarks under these Z3 twists become global
anyons and, hence, display different thermodynamic
properties. We further show that the lattice data can be
roughly modeled by a Nambu-Jona-Lasinio-type Lagrangian with
a minimal coupling to a constant gauge field A0=2πnT/3
(with n=0,±1), which arises naturally from the nontrivial
phase of the Polyakov line.},
Key = {Chandrasekharan:1995nf}
}
@article{Chandrasekharan:2008gp,
Author = {Chandrasekharan Shailesh},
Title = {{A new computational approach to lattice quantum field
theories}},
Journal = {PoS},
Volume = {LATTICE2008},
Pages = {003},
Year = {2008},
url = {http://arxiv.org/abs/0810.2419v1},
Abstract = {http://arxiv.org/abs/0810.2419},
Key = {Chandrasekharan:2008gp}
}
@article{Chandrasekharan:2006wn,
Author = {Chandrasekharan, S and Jiang, FJ and Pepe, M and Wiese,
UJ},
Title = {{Rotor spectra, Berry phases, and monopole fields: From
antiferromagnets to QCD}},
Journal = {Phys. Rev.},
Volume = {D78},
Number = {7},
Pages = {077901},
Publisher = {American Physical Society (APS)},
Year = {2008},
ISSN = {1550-7998},
url = {http://arxiv.org/pdf/cond-mat/0612252},
Abstract = {http://arxiv.org/abs/cond-mat/0612252},
Doi = {10.1103/PhysRevD.78.077901},
Key = {Chandrasekharan:2006wn}
}